I got Fritz 8 and a friend got Chessmaster 10, and after fooling around with Fritz and hearing what my friend said about Chessmaster, I decided to buy Chessmaster too. Since then I have I almost exclusively used Chessmaster, and I would recommend it much more highly than Fritz. The teaching tools are much more extensive on Chessmaster, and higher quality, and the computer opponents seem much more varied and interesting. The game analysis features seem comparable in the two, with Chessmaster making more comments, but I felt like Fritz's were a little better. In Fritz you can play through variations in the annotations and in Chessmaster you can't. Chessmaster has nice comments on opening lines, Fritz generally makes no comments at all until you're out of an opening book. Both came with 1 year subscriptions to their websites, and if you are interested in that, Fritz's has a much better community and interface. The chessmaster site is difficult to use and very sparsely populated (generally fewer than 25 people on it worldwide at any given time). Fritz's engine is supposed to be slightly better than Chessmaster's, but for me, they both kick my butt at way below maximum strength, so what matters more is how well they scale back that strength, and I've enjoyed playing Chessmaster's opponents much more. Anyway, I hope this helps you out.
(P.S. I agree that it totally sucks that you can't play chessmaster on Win2000, luckily I got a new machine around the time I was looking)