not quite sure, but believe you can only upgrade from Vista..if you are running XP then you have to do a new install. I've been running Vista for some time now and once I'd stopped all the silly things like AERO it ran as well as XP. I will not upgrade for about 6-12 months as I like the user found bugs to be ironed out first. One thing to remember is that new operating systems are mostly just revenue generators for microsoft. If they just tweaked their existing operating systems then their revenue stream would soon dry up.