you only need to limit the fps to 30. CPU slowdown shouldn't be necessary,
also see here ;)

Well, you should more careful before saying stuff like this, because as far as I know, I76.exe was designed to run at precisely 25 FPS, that's why there's a patch called 25FPS, it's not 23, not 29 and not 30, it is 25 exactly. Using that patch solved all physics issues I ever had, and for the first time after 20 years I could play the game without feeling like cheating against a handicapped AI.
Now, replying to the thread creator, DxWnd is a FANTASTIC tool, is a gift from god really, in this case god nicknames himself as Gho... Wow this little thing is a marvelous creation. I started experimenting it to play Delta Force 1 with mouse aiming in a window, and quickly I learned its framerate-limiting features and other neat stuff. Took me some time to realize that I had to enable Expert Mode in order to see all those extra features though. This little tool is so impressive that it even works on Linux using Wine (the windows "emulator") flawlessly. So far, I used to fix Simcity 3000 (map scrolling issues rendered the game unplayable) and more recently to limit framerates in Banished (a game notorious for causing overheat issues due to framerate being uncapped at menus and during pause mode). Maybe, according to your experiments over there, DxWnd makes possible to play I76 without the use of the 25FPS patch at all, more alternatives is always good news! Thanks for sharing this info!