I was encountering the "yearning for your next move" issue. To solve it I tried running DKII in Windows 98/ME compatibility mode but from then my campaign progress was lost along with the Pet Dungeon progress. I did not start a new game, because I feared it would overwrite the saves.
Starting it in Win2000 compatibility mode again did not solve the problem.

I run WinXP Prof SP3.

I have had my campaign wipe.

The solution is simple. Save at the start of every mission.

Nothing more annoying than repeating the first 8 levels because the campaign auto save wipes. I have not lost any of my saved games unlike with other games (fallout 2 has wiped all its saves before).

Hope the info helps.

Have you tried:

"> Run DKII

> Once the menu is loaded hold down ctrl alt delete

> Task Manager will open and the game will minimize

> Right click Dungeon Keeper click "Go To Process" this will go directly to
the process in the processes window

> Right click the process should be something like "DKII.exe" click "Set Affinity" this will open the "Processor Affinity" window

> There should be two "CPU" processes checked, uncheck one of them I always keep CPU0 checked and uncheck CPU1

> Close Task Manager and click the Dugeon Keeper II tab on the taskbar"

http://www.osnn.net/pc-gaming/97757-dungeon-keeper-ii.html

Sounds like it will solve the issue.

I suspect the problem is far more simple. If a game is storing its save games in program files, in later versions of windows it will use "virtual paths" to the directories. I think this is to circumvent UAC. These didn't exist in win98, so when you change the compatibility mode, it changes the save location (most likely to be something like directly under the install location). I then suspect that the save game location has been updated, and the new location then gets persisted when you change back.

If you take a look in C:\Users\<YOUR USERNAME HERE>\AppData\Local\VirtualStore\Program Files (x86)\GOG.com\<THE DK DIRECTORY HERE>\

then you'll probably find your old save files in a subdirectory, you'll then be able to load them again by copying them to the new save location, which will be under %program files%\GOG.COM\<YOUR INSTALL DIR>

This is all just a guess, but I'd bet pretty heavily it's correct.