I don't have the full details on everything that GOG have changed for this release, whether it just be wrappers or other fixes. The system requirements (which is what your thread started off about) would still be higher even with just DDraw wrappers, as they would require newer versions of DirectX than Windows 95 was capable of. So your initial question has been answered by various people on this thread, including a GOG team member (the first response).

The thread then moved on to discussion about support for older OSes. You even asked the question yourself:
To which an explanation was given and you responded that you want them " to not remove what was already there" even though GOG may well have had to in order to get it running on modern Windows OSes.

The evidence is all here within this thread for everyone to see, and again you call me stubborn.

But basically, if you want the original files, go get the CDs, I'm sure you can find them on eBay or in bargain bins for used, old PC games.

I'm confused. One of GOG's goals is basically getting old games running on new machines. What were you wanting them to do instead? If you want the original version of the game sans GOG tweaks/changes and can't get the files you need from the GOG version, I wouldn't rule out just pirating the original game (if you can't get it cheap off Amazon or eBay).

Windows XP no longer receives updates from Microsoft. That should make maintaining support for it easier than with later versions because you no longer have Creator's Updates, Anniversary Updates or Service Packs causing your code to fail. Or policy changes at Microsoft (e.g. tightening up of code certification requirements on kernel mode code) forcing a change of approach.

The justification here should be customer requirements - as long as there are GOG customers using WinXP (yes, I'm one of them) then support should be maintained (note I said maintained, not extended to new games). You don't have to look far to see developers and smaller companies providing support for earlier Windows versions (even the 9x series) so why should GOG be any different?
And this is a game released in 1996, 23 years ago. If GOG can support something 23 years old, then why the objection to supporting something 17 years old? Especially since the "support" comes down to "don't add anything that breaks it" (at least make such additions optional).
Not sure of the relevance here - you're talking about changes that had (mostly) beneficial impact (better quality recordings, more compact media). In contrast, every recent version of Windows has added more inefficiency, more user monitoring (yes, it did start with WinXP), restricted choice (e.g. requirement for signed drivers on 64-bit systems, Patchguard limiting users' choice of security software) and, to put it midly, "controversial" UI changes.

Now if anyone can confirm that this release will work on WinXP, that's great. But even then, GOG has developed an unhealthy habit of breaking compatibility with later updates (see this thread for examples) so a change in official policy is needed (I currently have support tickets outstanding on 4 games which have been broken so far).

What happens to WinXP today will occur with Win7 and later versions tomorrow so this is an issue that should concern every GOG customer.

Not necessarily. Because XP no longer gets updates, those old methods and libraries and such that XP has won't get fixed for newer hardware and software and will eventually just stop working. 16-bit software is pretty much dead in the water as most Windows are now 64-bit with no support for 16-bit as part of the OS, so they have to rely on emulation, like DOSBox. Some library files within the games themselves may rely on Windows libraries that have since been re-written, replaced or removed, so won't work as intended (if at all), so the game may need a fix applying in such scenarios, a fix that makes it use newer OS library files that don't exist on older OSes and so will no longer work on older OSes like Win95 and WinXP.
Microsoft don't even support their own product here, Windows XP, so why should anyone else? If some developers choose to then that is up to them, but once the OS creator stops supporting the OS, nobody should be obliged to support it for anything. For GOG, they have a limited number of test bed machines on which they look for issues with the games that they distribute. They aren't going to keep installing unsupported Windows OSes on them.
Because GOG's business model is getting games running on newer OSes. Yes they also now release new games and some indie titles, but historically they started off as getting older games running on newer systems. They aren't interested in getting older OSes running or supporting the running of games on older OSes. Note also that GOG do not support the old game itself (they are a distributor, not the developer of the game). They often rely on DDraw and Glide wrappers, unofficial and community updates and patches, emulation, no-CD patches, Windows compatibility fixes, etc. Adding some of these changes to the games to get them working on newer OSes will break them running on older ones.
The point of the other examples I gave were to show that technology changes with time and older tech drops out of use and support. You either move with the times or you accept that you aren't guaranteed of any support for your older technology.

No, I copied the whole folder with its subfolder.

I'll try to perform more tests, on real hardware, but that will have to wait a bit.

Stupid forum filtering has been blocking me from making a properly reply here - please bear with me.

(apologies for delayed reply but a misplaced tag resulted in the forum blocking this post)
This isn't an issue likely to concern games (or other software) released prior to or during XP's support period.
DOSBox is included with those games that need it, so GOG is effectively supporting them.
It was only with Vista/7 that Microsoft started to break compatibility in a big way - pretty much anything from the 9x era will run on XP and the only example of a library I can think of that was removed would be WinG. So for games from the XP-"era" and before, this argument doesn't hold water.
If MS is no longer changing anything on a specific version of windows, then developers shouldn't need their support on it - they can, in most cases, work around any issues that arise.
If they only have 3, as the second post suggests, that is clearly inadequate. But their willingness to support Linux, which has similar or smaller marketshare to XP according to both StatCounter (XP 0.71%, Linux 0.79%) and NetMarketShare (XP 3.91%, Linux 1.45%) suggests that "official" support (only available for a small subset of distros in Linux) is not a factor, not a small audience. Given that the support requirements for Linux (with its considerable variation in graphics, windowing, file management and security subsystems) should comfortably exceed that of monolithic WinXP, one has to ask exactly what commercial consideration is behind such decisions.
XP is still listed as a supported OS on many games (e.g. Shadowrun Hong Kong) so its age is not an issue.

This bears repeating - I am talking about games that preivously worked under Windows XP rather than new content where the developers have decided not to offer WinXP support. In these cases, GOG has to expend effort withdrawing compatibility (and has been doing so without informing users on a game-by-game basis so far).
No-CD patches would be designed for the original target OSes and shouldn't break compatibility. The vast majority of other items work within XP and when an example arises, is it really that hard to make it an option during install?

I guess the real question is, Are you actually still using XP and why?

Because XP habe been a dead OS as far as support goes for nearly five years now,and it's not worth GOG;s time or money to support it?
XP was a great OS, but it's time has passed (they never could get it work well with 64 bit,the 64 bit XP was a disaster)
As for the requirement being highter for Diablo now hten they were in 1996, I suspect that has to with the changes necessary to make it run ona newer system.

We have sort of an XP cult here at GOG;they hate all Windows beyond XP.
People forget when XP came out a lot of people bitched about how much better Windows 95/98 were.......
If you want to have a dual boot or us a Vistural maching to run XP, fine. But it's simply no longer practical as a preimary OS. FOr one thing, that XP never really worked well, despite Microsoft's efforts, with 64 bit for no other reason.
Hell you have people here who despise Dos Box and other DOS emulators and only use original Dos.

BTW never ceases to amaze me that so many self proclaimed 'Old School Gamers" are so ignorant of how computers and OS's work. Seems to me if you really old school you would learn something about that.

That ia much,much, more legitimate question then "WHy won the GOG version work on my legacy machine?".

Because I prefer it. You want more detail, read this thread.
As long as an OS is in active use, it cannot be described as "dead". And XP is seeing wider use than Linux (see above usage figures), excluding Android. And GOG's support costs for Linux probably far outweigh those for XP, especially given that XP is now static.
Windows 2000 was the "great" OS in my view - XP was where things started to go downhill (product activation, cheezy UI themes, control panel "categories" making it harder to find configuration settings). However, XP can be configured to override most of the annoyances via registry settings, and XPLite and nLite can bee used to strip out the most annoying (and most dangerous security-wise) elements.
As someone who was around at the time Win95 launched, my memories were quite different. XP got (and still deserves, as do later versions) flak over Product Activation but was praised for offering better compatibility with older software than Win2K. The willingness of many here (of all places, irony) to overlook product activation though is tribute to Microsoft's ability to ram features down consumer's throats.
If you tried a virtual machine, then you'd be aware of its downsides (specifically inability to directly access hardware like graphics cards) that renders it unsuitable for most games.

And thanks to Physical Address Extension, 32-bit XP can address up to 64GB RAM (I'm using 12GB for ramdisks and 32GB for a disk cache on my 48GB system). So less need for 64-bit Windows and all its architectural idiocies.
It is precisely because of OS knowledge than I'm staying with XP. Have a look at "A Cost Analysis of Windows Vista Content Protection" at here for a starting point (yes, it focuses on Vista and yes, it still applies to later versions).

Because microsoft can't do better, I have yet to find a satisfying linux distribution that replaces it and macos is insulting (also microsoft tries to become like apple, which explains why everything goes wrong).
I have 7 installed, so I am legitimate in my complaints. Deal with it.
I use XP because no matter how much FUD goes around, I still know better than weak minds attracted to new&shiny or who give in to peer pressure and what should be called swindle.

Crossing fingers for ReactOS, but I wonder how old I'll get before it's ready, if ever.

Yes it is a concern. Many old DirectX games (DX6 for example) require wrappers for modern OSes otherwise they have issues (like rainbow colours) or crash a lot, or don't even run at all. These modern wrappers won't run on older OSes. dgVoodoo2, for example, only supports Windows Vista/7/8/10. I don't know if GOG have started to use dgVoodoo2 within any of the games that they distribute (the 3DFX games I have from GOG all use nGlide) but it often gets recommended by users within the GOG forums for when nGlide isn't working for someone.
Yes, and the point I was making is that third party software is being used to make them run as they won't run natively on modern Windows OSes. If DOSBox ever gets an update that drops support for XP and GOG start using it in the games that they distribute then they won't run in XP any longer (and it would be up to the user to replace it with an older DOSBox as they are running on an unsupported OS). Note that these old DOS games are running wholly within DOSBox, so mostly it is the DOSBox installation and settings that GOG are supporting here, though there are a few instances of 3DFX wrappers used in conjunction with DOSBox.
Yes it does, as described above. GOG try to get old games running on newer OSes, so a Win 9x game, whilst it may run fine on XP, probably needs tweaks for Vista, 7, 8 and 10, and that's what the GOG distributed releases would support, not XP. In fact, Vista support is also dropped (Microsoft ended Vista support April 11th 2017).
Why? Developers may want to use up to date software and hardware in order to take advantage of newer features, but these may not work on old, unsupported OSes. Rather than write multiple releases for different OSes, it would just be a case of dropping support for the unsupported OSes.
You are assuming one test machine per OS, which is a fundamental error. I don't have an up to date figure but the last time I saw it mentioned by a GOG staff member there were around 30 test machines, with varying hardware and OSes. This was quite some time ago so the number may have changed since then. As for Linux, there were a lot of users who kept asking for Linux releases and eventually GOG were able to find a way to provide some Linux support.
Now this is something I can agree with you on, but it isn't something new to GOG. I remember when GOG started replacing all of their original installer packages with new, revamped ones, and requirements were updated on most games at the time. I'm sure that there was a GOG announcement about it at the time. I imagine they were retesting the newly packaged installers on the test machines they had at the time and that's why their requirements changed. This could well still be happening, albeit at a slower rate now.
Again, it depends on the software being used, but for GOG to provide an option during install so as not to use this software (in order to run the game natively within WinXP, say) would also require GOG to test the game on WinXP, which they won't do as it is now unsupported.

DirectX9 supports previous versions (I have for example, no problems running DX5 games, unless the graphics drivers somehow break them). Now if the DX9 implementation in Vista/7+ doesn't work properly, that is a problem that should be raised with MS.

If course, if MS knew about these issues and haven't fixed them for several years, then that does raise the question of what their support is worth. And the wisdom of moving from an OS where things work to one where many don't.
dgVoodoo2 is the only example I've come across so far, and its OS limitations are an argument for making it optional.
Then we would be having a simialr debate in the VOGONS forum. But it hasn't and the fact remains that games running under DOSBox wil work fine in XP - and Win2000 - and very likely WinNT.

Plus this project, despite not charging for DOSBox, support 6 different OSes (32-bit Windows, FreeBSD, Fedora, Mac OSX, RISC OS and Debian) for their latest version (and 4 others with older versions) which makes them an example that GOG would do well to imitate.
So they can offer a "tweak free" version as well. In fact, I think it would be an excellent idea for them to include an image (zip/rar/iso archive) of the original files or CD/DVD-ROM - no installer or tweaks, for expert users and gaming historians to use. Cost - minimal.
We aren't talking about new games here (though Visual Studio 2015 can be configured to produce WinXP compatible code - see here) but existing ones that already run on WinXP. New hardware isn't an issue (unless you're considering something ambitious like adding Oculus support to Duke Nukem 3D...) so neither should software.
I did prefix that sentence with "If"...
If they have as many as 30, then having WinXP installed (or installable) on a couple shouldn't be an issue. And Linux support is both more complex/costly (due to its greater variability) and likely less rewarding (due to the smaller report online usage) than WinXP. Nonetheless I think Linux support should be retained.
There are two approaches - one to provide the raw game image separately from the "enhancements" (which would also fulfil the original files request above). Or have a script (which GOG does now use in their current installers for things like Start Menu shortcuts and registry editing) which checks OS and only applies patches that have been tested against a specific OS (ideally, leaving the patch files somewhere for other OS users to experiment with at their own risk). That would avoid the need for testing on "unsupported" OSes.

I mean, XP Pro is my favorite OS ever, so I understand your sentiment, but I've had to move on a long time ago, because it's just outdated and it's bascially not supported in the industry anymore. I went from XP Pro to Max OS and Linux, now I'm on Windows 10 and it doesn't seem all that bad.

Edit : Anyway, wasn't trying to hijack, I just didn't know there was a whole cult of people still using it as a primary OS. o.O
Thanks for the explanations.