I assume the standard INI fix (change bUseThreadedAI=0 to bUseThreadedAI=1 and insert a line iNumHWThreads=2) has been done OP? That is meant to resolve freezing and crashing though not stuttering and tearing.
I can't say I've experienced stuttering in Windows 7 x64 or Windows 8.1 but I had another issue on the weekend - despite the game working perfectly the week before and nothing changing, I tried to run it on the weekend and would get instantaneous crashes without even seeing the loading screen. The only way I've fixed that one is to use D3D9Gen to create my own D3D9.dll file and put it in the game's directory. Annoying as anything.
EDIT: You'll never believe it. I've just deleted my custom-made D3D9.dll file, uninstalled Microsoft Silverlight and the game is working again like it was a week earlier. No help to the OP I know but worth sharing for anyone else reading.