Windows Vista will be better for the security for documents. But I doubt that it will be better that microsoft Xp because the windows Vista failed to present advances to make it better and secure. and besides the beta version have been leaked alreay to wares and other P2P. My advice to you is stay with Windows Xp
Well the best anti-virus that I have seen and work with is Norton Corporate Editions. They dont hog any ram (norton Antivirus) and they also search for spyware and adware.
Well the P2P sharing programs offer a lot of spyware (kazza, etc.) that slows down your computer by upto 75%. If you want to get a sharing program I suggest Limewire because its not spyware and no ads. Shareaza is also a good one to get for the share program because it has connections to every P2P program.
sadly I must say that they found a way to get the validation with a crack.Personally I dont support the piracy but I must say that there is always a way to find a way to get through microsoft obsticles