Tonight I spent an hour or so trying to get my old XP laptop working with my Apple Airport Extreme base station. For some reason it would get stuck at acquiring network address and never connect to the WiFi base station.
It would work fine without the encryption, but I just don't roll that way. You won't catch me with my encryption down, especially with a Windows box on the network.
At any rate, it turns out that if you set your WPA2 password to have exactly 16 characters in it, then the XP box can connect. Note that the Apple computers and iPhones on my network have no trouble connecting with WPA2 passwords less than 16 characters long. This sounds crazy but it was easy enough to test, and sure enough, it works. So I now have a 16 character WPA2 password on my WiFi network. I suppose that's at least more secure than the shorter one I was using before. Maybe Windows really does encourage more security after all. :-)