I just recently went through the same thing. Here's how I solved it, with help from previous threads.
Alter the shortcut for CMBB to be something more like this:
C:\Windows\System32\cmd.exe /c start "CMBB" /affinity 1 "D:\Program Files (x86)\CMBB\Barbarossa to Berlin.exe"
Change the location of the executable to wherever you have it installed.
Also, run it as administrator with Windows XP SP2 compatibility.
2nd, once you get into the game (for me, all the way into the 3D map), hit your "Windows" key. The game should go out of the forefront. Alt-tab back to it, and hopefully the framerate will be good. Note that others have just been able to alt-tab. I can't, because it crashes on me every time. The windows key works fine though.
Hope this works for you!