Sorry to resurrect an old thread, but I saw a bunch of referer logs from here so I thought I'd pop in. I'm Ron Parker, creator of the Font Thumbnail program linked from the first post in this thread.
It doesn't actually work in Windows 7 without some registry hacks, due to the fact that my installer registers it in a way that causes it to take a back seat to the built-in font thumbnails others here have mentioned. I'm a little biased, so I do prefer my thumbnails to the built-in ones, but chances are if you've installed this on a Windows 7 machine you won't see any difference except for .pfb files (which Windows 7 doesn't thumbnail for some reason; it does do the associated .pfm files, however.)
If for some reason you did want to use my thumbnails on Windows 7, you'd want to delete or (preferably) rename the following registry keys that point to the built-in thumbnail provider: