Old games from the windows XP era sold on GOG.com works perfectly on old computer running the OS.

The offline backup/installer is the same for all the versions of windows, you can put the files on a USB stick and use them to install your game on any old or modern machine. I have an old Notebook ( without disc drive ) and I have installed many games this way.

The only exception, at least for me, are the games running with DOSBox. I'm having an hard time running them properly but it's not because of an OS incompatibility, more like because my laptop isn't powerful enough. I think the minimum system requirements on the store pages are wrong or somewhat misleading because they are the same for every emulated game.

Sorry. I wanted to reply to Fergei, but I mistook your for him because your avatars are the same and I replied to you instead.
My bad.

To answer the OP, it is possible. Even the Steam games too.

You obviously can't expect the same level of support, or whether the compatibility will be a problem, but in general, downloading and installing is not the issue.

I’m using WinXP, and older games that originally ran on XP are generally fine on it, even if described otherwise in the store pages. As for specific games, I think you can check or ask in the corresponding sub-forums before buying.
DosBox games are generally fine.

I tested it, the installer offered on GOG of Civilization III runs fine on XP. But as mentioned before, when GOG updates installers, it might break compatibility with XP.

This is not accurate; SOME games that came out for Windows XP work, but many do not. Games like Star Wars Battlefront and Crysis most certainly do not work.

Why would you post to correct a post that is over 2 years old when that information may well have been accurate at the time of posting?

Many games that originally worked in XP do not work in XP via the GoG versions; if it is a non steam game; always go for a disk version over gog's hit and miss for XP.

Asterisk. You can certainly try to install them, but don't expect any real help for 20 year old operating system. Good luck trying to track down system libraries for an operating system introduced before the Nintendo Game Cube existed.

Also, I'd like to give charlemagne1980 the "I'm not listening award" for necromancing a thread twice while not actually contributing to it.

Nice try; directly addressing the issue in question is quantified; here's your tater award.

There are games at GOG, that used to work with XP, that GOG have eventually updated to support newer Windows, often making them no longer run on older ones. GOG's main focus is making sure the games they provide, work on latest Windows, DRM-Free.

So as every year goes by, unless you have access to older installers from GOG, less and less are working with XP.

I don't agree with the situation, but I understand that GOG has to reduce costs wherever it can, and most folk, increasingly more, are not going to be bothering running a game on Windows XP, and before long not Windows 7 either.

The worst thing really, is that GOG don't give us access to older versions of the games we own. That doesn't help with newly added games to their catalog of course, but it pays to download as soon as you buy.

nvm

If that's the case then a repository to access old gog installers would have been great.