Stuff: You might try right clicking the game shortcut, click Properties, click the Compatibility tab, select the compatibility mode for Win 98 / Win Me and check mark "Run this program as an administrator" first. See attached image . . . =)
Did you install the game as an administrator? Are your video drivers up to date?

Figgles: Aha! Installing it in a created directory helped...I actually did the same thing for Planescape Torment (which unfortunately isn't on GOG :( ) I guess I should just install every old game outside of program files from now on.
THANK YOU!

wcellison01: I have completely solved this issue on my Vista notebook. Here's what I did.
1) I installed DD to a directory outside program files (probably not necessary, just turn UAC off as a substitution). *This step by itself did not help the game run faster, but it did make the installation possible*
2) Download the old config tool. I don't care what the developer says. This fixes it for me.
3) Replace the current config tool with the old one.
4) then change the setting from Direct3D to DirectDraw or Glide.
On direct3D it was 6FPS, Draw was 16 (still unbearable), and last but not least Glide put the game up to 30FPS which makes the game definitely playable. (to find out the FPS just run the test in the old config tool) There is a link to the old config tool earlier in this thread. USE IT!!!

Figgles: And If I delete the new configtool to replace it with the old one, the game won't even launch.

schmea: Such a shame, it looks like a really deep game... just what I enjoy.

schmea: ...

Stuff: You also tried the compatibility mode in other modes besides Win 98 / Win ME?

The slow problem seems to pop up on certain systems from time to time without a real single solution being found. I found that I needed to ALT-TAB out of the game start screen and OK some run permissions for my firewall (Comodo), It would close the request when I closed the game so I could never see the request without ALT-Tabbing out.

Some folks have fixed the problem by backing up their saves, uninstalling the game and reinstalling in a directory outside of Program Files. Seems UAC directory security can block access to hardware for a game installed there. You might try turning UAC off and trying some game play, if the problem is gone then installing outside of the Program Files directory is probably a solution.

Using the AMD Dual Core Optimizer may help some graphics problems (I believe you are running AMD?) It helped me with some stutter problems on my laptop.

You can set the affinity to one core manually, if that helps with the problem try using RunFirst to set it automagically for the game without doing it manually. I use it on my install and it works well. I didn't have any problems, I just wanted to try it out before I recommended it . . . just left it after setting it up.

Some folks have solved the problem using the old DD configtool.exe to set rendering to DirectDraw instead of Direct3D See this thread. You will see an early post in that thread from DeathKnight (a DD developer / programmer) explaining why they removed the option and plainly stating that it is not supported any longer. It is something that you would try at your own risk. It would only affect DD.
This link used to be good for the old configtool.exe Like I said, use at your own risk and some have claimed it fixed their problem.

There is always a chance that I have misunderstood the extent of your slowdown. Pressing the "R" key for always run will speed up your character a lot. Thought I had better add that . . . =)

hrasan: ...