Has ANYONE ever been able to play HoMM3 WITHOUT access to the internet? I bought this game for my dad to play on an older PC of mine (Well within the specs to handle the game) but after a few days of successful gameplay, the game always seems to just magically kill itself. Suddenly he goes to fire the game up and it hits him with "You are offline, some parts of the game may be unavailable" And then "No game found." The man did nothing out of the ordinary. So one of you wizards please come along and assist me with this. The AI customer support is useless as hell.

I mean is there just some kind of software in there designed to terminate the program? If so I'm just gonna have to resort to other means.

I never allow HoMM3 access to the Internet. I have never had a problem like what you describe.

Are you trying to start the game directly or through GOG Galaxy? I never let Galaxy touch this system.

Yes, the chatbot is useless. You could try opening a support ticket. That's not very useful either, but at least you can get a human to fail you instead of a chatbot.

Thanks for reaching out Brother. Essentially what happens is I bring the ol pc up to my internet equipped house and go through the usual bells and whistles when it comes to downloading the game. Download GOG, sign into GOG, install the game and then proceed to play it once for test purposes and then send him home wheres there's no internet. Only every time we've done that (a grand total of 4 times now) he gets like 3-4 days in and boom, games utterly GONE. I mean I open the files and everything its just -poof- gone. Its the weirdest thing ever. Never once in my life heard of a self terminating game. I can only assume it has to do with GOG, though I've learned with PC's not everything is as it seems.

UPD Here is the links from Galaxy offline backup download game subpage or normal browser web version of GOG Account Library game entrie
http://www.gog.com/downloads/heroes_of_might_and_magic_3_complete_edition/en1installer0
http://www.gog.com/downloads/heroes_of_might_and_magic_3_complete_edition/en1installer1
to the GOG versions of HoMM3 (Eng two parts)(similar link for Fr/etc and for Heroes Chronicles 8x1 or 8in1)

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GOG Galaxy =/= GOG in both ways. GOG Galaxy version is still DRM-free usually (very very few exceptions) for offline content.

So you mean you install GOG Galaxy. Then there is two way. Use it as downlader for normal setup offline installers (GOG Galaxy client is default but completely optional way in both game builds or way to download offline one build UPD: links above). Install technically drmed Galady version (theoretically Galaxy itself is DRM although exes remain drmfree). Galaxy same as all client (and BT too) require validating at the end.

In way how you describe it - moving to another PC. No. There is only two what-who can them removed. User itself. Or "good" nowadays mobile backported Windows OS. Especially after sometimes more errorenous updates. And TMP2.0 decided what files are should be on your PC (Windows 11 at some update become DRM itself entirely).

There is no way in any OS exe file can kill himself erasing it.

Technically there is only one program installed on any computing devices/OS mobile too. OS itself. Anything else is components of it. First off any games working states is how OS run it.

There is also access impossibility to erase running exe, but few DRMs actually dublicate it to AppData/ Temp folders. Still parent process in use. Galaxy can do that after game close. But back to main story - there is no Galaxy on second PC?

Or it was. Something tell it cant get internet access. No drm leftovers in Heroes3 (if gog did brin drm which they never do) can say that exactly in that manner.

Back to story. GOG Galaxy version is DRM-free itself. Not 100% but been installed you can uninstall Galaxy and run game directly by exe.
(again, GOG version is another one separate from GOG Galaxy one).

Galaxy client can find (wrong or right) game installation corruptable and run validate process which move some files to temp folder. But Galaxy didnt force actually checking game state. No for corruption no for up-to-date. Some promts will appear and user must click on it.
That can happen with or without online connection.

If it is not come from Windows OS decising delete some file. Or 3rd party cleaners including running in background or Task (to run PC clearing process time to time)(it can decide game been uninstalled but game folder stay with many "unneeded" files). Then it is come frkm user. Maybe Galaxy show some promts. But it is user at the end.

For Galaxy client and version must be connected to internet and validate installation. Better at least twice (for long time client no more report result of process and ALWAYS redownload something).

For offline version must be reinstalled from offline setup file.
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I did play in offline version moving it from another PC without installation. But didnt test it without online.
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Steam working worse. I did play tne game in offline mode steam (more better mode - "no connection" just turning off network on notebook without switch steam offline) for a week. And at weekend it suddenly going unavailable. BAck to online Steam decise game need to be validate or updated. Not 100%. For a game didnt get any updates actually.
Of course Steam not allow to stay on installed version as always he did. GOG Galaxy client by default stay on installed version and suggest update it. And unlike Stean there is individual option for each games switch that way - force update, default or never update stain on old version +rollback function if needed (set exact version in game properties and Galaxy will stay on it).
Ofc games srill DRMfree and launch it from exe dont care about updates and their settings.

BTW. If you interest in Heroes Chronicles. Using browser you can download better older 8in1 version but no GOG site not GOGDB do not provide direct links for it (offline setup file i mean of course)(GOGDB for no reason make file list un-clickable removing links, you must take it from GOG API page on GOGDB). Manually copy and edit link allow to download it.
Same as uptodate 8 separate installers.

As the previous respondents wrote, much of the game is out there in GoG's galaxy, not on your old PC. The game will run happily offline. GoG galaxy will not. Download and run the backup installer for a self-contained copy of the game. (I find it best to RIGHT-click the link then select Save link as... This lets me put the installer straight to where I want it instead of having to retrieve it from my Downloads folder.)

By the way, from what I have read, the installer creates a sub-folder for the game: DO NOT LET the installer put the new folder inside C:\Program Files, C:\Program Files (x86), C:\Program Files (x86)\GOG Games or anything like that. With modern Windows this is asking for trouble. Maybe it would be OK on your older PC but why risk it. Override the default to have a C:\GOG Games or something. (If you partitioned your drive to have a D:\ (for example) as well, use that.)

When you download offline setup move to folder like (if it is in differ one)
D/Downloads/GOG/might_n_magic/heroes_of_might_and_magic_3_complete_edition/
check setup exe file for Digital sign tab and "sign is valide" information.
Run it as admin and in setup options make sure validate integrity is check on.

Or connect to online restart Galaxy as admin and validate twice. But looks like offline are better variant for swapping game.
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By the way installing validating and run once is a good way to deal with client-based game versions. That required for Galaxy too cause it get condigured at first launch. Admin mode required for galaxy exe for proper installing. As i see, OP on his side did everything alright and have experience to deal with it.

As user above say installpath very important. Not only program files but as he say even non-C drive are better.
Clients and games should be in path like D/Games/Steam/
X/Games/SteamApps/common/
X/Games/GOG/ (for client and just Games for Games better without subfolder).

When possible also better use non default game folder name. Game-name-1. Latin letters and arabian digits. No special symbol,s umlauts/cyrillic/unicode, spaces, "_". Short name with short no-subfolder path. X/Games/Warhammer-40k-DoWSS or -40k-Soulstorm or -40k-SS. Actually long names ok too even for Win9x games on 2Tb drives. Never faced "not enough space" issue or inpossibility to put such path into installer. Same rules, not so long name folder still. For example of Wh40k Dawn of War Soulstorm exact full name folder indeed too long. Just a bit long.
Same for some Might and Magic games with their long names. And creating subfolder make worse.
D/Games/GOG/Might-n-Magic/Heroes/HeroesofMnM_3_Complete is a bad example.
D/Games/MnM/Heroes/H3 also wrong cause of excessive subfolders.

"_" symbols actually better as minus "-" especially for DOS/DOSBOX games.

GOG offline installers better even for GOG Galaxy. They allow install it to custom installation path with custom ahorter name without spaces. Then validate+update through Galaxy and you get better Galaxy-based version than in Galaxy itself.
No any client/installers/discs default paths should be not used. Never.

Along with UAC-VirtualStore issue there is else unrelated issues. One of them is skipping installing empty 0bytes files or empty folders. Without errors cause setup's check integrity errors files and not validade installation post-install. You even not realise there is something wrong wit installation before issues come.
Happen more often on non-Windows. Or on Windows when installing games from img files by build-im mounting disc images app. Normal virtualdrive with driver required.

Update: Done everything as mentioned in previous posts above, even tried different PC's to the same effect. Simply put, HoMM3 does not and will not work offline period. If you've somehow managed to make that magic happen yourself, than consider yourself some kind of grand wizard. I can humbly say to anyone considering buying this game through GOG as medium to spend your money elsewhere and try getting your hands (if you can) on a physical copy.

Considering you're the only one with such problems, I'd say that it's nothing wrong with the game, but with your system/workflow.

None of my games have internet access and they all work fine (no Galaxy installed, of course).

Another thing I strenuously avoid is Microsoft's OneDrive.