Winamp is by far one of the most stable applications I've ever seen for music. If it freezes, this is typically a hardware issue or a bad plugin installed. I'd suggest trying the uninstall/install deal but make sure and delete the whole winamp folder from the hard drive. I would also suggest a disk check while at it..
You should also try playing the same MP3s with another player or front end to see if the machine freezes at all.. if it does, chances are it is a hardware issue.