I wanna build an old PC for nostalgia sake and I want to run some GOG games on it. I know that the installer won't run on win 98, but I could install it on my windows 7 machine and then copy the data to the win 98 machine.
I used the search and found two topics like this here, but they both covered dos games, not windows. And the consensus was that old dos games will run on win 98 from GOG.

What about windows games tho? Stuff like Giants: Citizen Kabuto and Planescape Torment. Will those work? I know that some re-engeneering may have been done to get some games to run on modern machines which could cause problems when trying to run them on old OSes, but is there a chance some will work? Or is there some common code in all of them that will stop them from working all the time? (except dos games which would be different on win 98).

Basically what I am trying to say is that I am aware games may be modified in different ways to make them run on modern machines (or not modified at all), but will there be a chance of them running on a game per game basis, or is there some common stuff that will make all the windows incompatible?

Has anyone tried with a non-DOS game and succeeded?

GOG's Unreal Gold works on my Win98se box. It was a version 1.0 installer and the engine was run in software mode. I haven't gotten around to trying any others yet.

edit:
It been a while but I probably didn't use the installer. I may have just extracted the files with 7zip.

Great, that means some will work. Thx

You mentioned GOG Planescape Torment. For giggles, I just installed it on my Vista box without running it and copied the resulting game folder over to my Win98se machine. I then held my breath and double-clicked torment.exe. It launched, played the opening videos, and I was able to start the first section of the game. I don't know if compatibility will hold out for a whole play-through but it seems promising. :)

Some games need their registry keys to exist so you might need to track the changes (regshot works really well) and replicate them on the other system. Most games simply make whatever keys they need if they are missing so this isn't a common problem.

Great!! I can't wait to try that!
For the record, I am building a machine with a Pentium 3 1.4 Ghz, 256 MB RAM and a Geforce 2 Ultra 64 MB. And of course using Win 98 SE.
I'm aiming to play games between 1997 - 2002. And I hope I can get Unreal Tournament to run online on it.

I haven't tried this software myself, but ran across it and...it looks promising? I don't know, check it out.
http://www.wikihow.com/Install-Your-Favorite-Games-on-a-USB-Device-and-Play-on-Any-PC-With-Prayaya-V3

edit : crap, nevermind, it appears that Prayaya requires at least Win 2000 in order to run...

I have nothing but respect for you for doing this.

I also have a Win98SE machine, a PIII 500MHz which I was keeping around specifically for old DOS games like Tex Murphy. But now I have them on GOG and the PC is gathering dust...

Thanks for posting that, it's a useful little program.