I think the PowerPrep software is floating on the Internet - I'm pretty sure you can find it on torrents or sharing sites. I can't give you a specific link right now, but:
- it doesn't work on some versions of Vista, not even when you run it in compatibility mode (I could not make it work, at least; I'm no computer whiz though)
- it contains a few repeats from the OGs
- it's generally seen as slightly easier as compared to GMATprep.

I just went through the GMATprep software's Math Review; it was a great little math refresher, and you can go into as much or as little detail as you wish, depending on you up-to-dateness on the concepts. I scanned through the main topics and found 2 or 3 little concepts of which I couldn't quite remember the details.
Just thought I'd advise everyone to check it out, it's very useful for those of us who haven't had math classes in a while!