XP ? was good in past BUT now ITS Windows 7 you try you love it. Like me i do now.
Pretty light and fast for a OS and old pc can enjoy it its like feeling to got a CORE I7... If you dont feel that its either you that .... lol

or its me that i did install great my Windows 7.
Vista is great also no problem, similar to Windows 7 just few changes
XP aint bad but if you can afford a new OS or want a new one then look my first word into up and you can choice a great one.
Mr.Agent