I use UTorrent 2.2.1. It is stable and it doesn't give me any problems with Windows 7 pro x64 at all. The only problems I have is when someone with 3.0 or later they aren't connectable to me. I hate it when users use 3.0 or later versions of Utorrent. Seriously those versions are almost always banned in private torrent sites or users should be discouraged to use anything 3.0 and later. The versions SUCK PEOPLE. Of course that's my opinion and a lot of others opinions.