I dont understand, you have a pc that runs xp yes? so why cant you carry on using it? is it a dodgy copy or something thats expired?

You can buy xp brand new for £60, but personally ive gone from xp to vista 3 or 4 times in the past and every time ive come back to xp for one reason or other, mainly because simple tasks that were a dodle in xp were impossible or just didnt work in vista.
Vista will not give you any benefits really unless your a gamer.