doesn't really matter from were u upgrade i mean all an upgrade does is carry over your programs and personal folders.if ur anything like me all that is ether backed up or installable anyway.i think the more focus should be on running win 7 smoothly with your current pc power what ever that may be.

i just say this for you are going from xp things are getting alot more demanding from there.my little lappy is a dual core at 3 gigs a side kinda deal and its all it can do to run win 7 ultimate.