If you haven't installed Mok's unofficial patch (and you're running the English version), please do so. That should fix it.If you are running a different localization then you'll need to find updated versions of BINKW32.DLL and SMACKW32.DLL and put them in your MM7 folder. You probably already have these files on your computer somewhere.
If these solutions don't work then there's something odd with your your graphics system -- probably with the drivers your using on your hardware. If so, we'll need your specs to go further.