Buying a computer sometimes can be stressful specially when you need something tailored for your needs.
Windows: The future
Windows XP’s successor, Windows Vista, is expected to be released to the public in early 2007. Keep an eye on eBay for the first available computers with Windows Vista.
Windows Vista will come in seven editions: Starter, Home Basic, Home Premium, Professional, Small Business, Enterprise and Ultimate. Features will include a Game Performance Tweaker, Podcast creation utility and online "Club" services giving exclusive access to music, video and privileged customer care
My recommendation is that you wait until 2007 to then buy the vista, as you should probably guessed the windows operatives systems get easier and easier.