It is unusual for me to be promoting Microsoft products due to the fact i quite dislike them *the only reason i have used windows is compatibility* but I will reccommend that you all try the new Windows 7 BETA build.
It will only work until August 2009 but is still well worth it until then. It is a huge improvement over Vista.
Also there will probably be hacks to make the BETA run longer. Which obviously I can’t promote, but cannot stop comments 
You can download Windows 7 here :
http://www.microsoft.com/windows/windows-7/
Check it out