timppu: I found it in one extra place under HKEY_USERS, but changing that didn't seem to affect it either. And to me it seemed that if I changed either, it would get changed in both at the same time ("HKEY_USERS\<USER>\" and "HKEY_CURRENT_USER\"). ...
Does the registry change work for you guys? ...
That both keys change at the same time is normal, as they are the same keys. HKEY_CURRENT_USER is just a link to the real entries under HKEY_USERS
If you're searching the registry with a non-administrator account, you aren't allowed to see the Administrator entries, hence searching only yields the entries of the current (non-admin) user. But remember this is only an issue, if you run the game as another user.
As for your question, yes, it runs in windowed mode at 640x480 on my system. I looked a bit deeper into this, to see what doesn't work. Try the following setup:
1. For testing, disable Windowed Mode in the registry again
- Open regedit
- Go to HKEY_CURRENT_USER\<USER>\Software\Bullfrog Productions Ltd\Dungeon Keeper II\Configuration\Video
- Set "Screen Windowed " to "0"
2. Use ..\Dungeon Keeper 2\DKII.exe to start the game, and not the Desktop link or any other executable, because GOGs safemode hack seems to ignore some of the registry entries
- Don't use Compatibility Mode and don't run it with another account for now
3. If the game starts with DKII.exe, but you get a black background in the main menu or a crash, hardware acceleration might not work
- Quit the game and go to regedit again
- Set "Engine Id" to "4"
- Restart the game and check if the background of the main menu is there. Quit the game again.
3. Back at regedit:
- Set "Screen Windowed " to "1"
4. Create a shortcut to DKII.exe (right-click) and open its Properties (right-click the shortcut)
- Add the following command line parameter to Target: -32biteverything
Target should look like this (depending on your installation folder of course):
"C:\GOG Games\Dungeon Keeper 2\DKII.EXE" -32biteverything
5. Run the new shortcut