@OP, your comment about Chessmaster being crashy caught my eye. That hasn't been my experience, so I guess I have to ask the obvious question - Did you apply the patches for Chessmaster? (Also just curious about which version of Chessmaster you had and what operating system did you use (and the OS you have now)? And do you still have your Chessmaster disks?)
By the way, there are lots of good suggestions so far in the thread. (Well, except for Chess Titans...sorry, Jion_Wansu )
Lucas Chess. Coupled with Scid vs. PC, there is little reason to ever use anything else. Both free.
Lucas Chess is good, but it's crashy.