Hi matey
have you tried just reinstalling vista?
the outgoing o/s has a habit of slowing down, clogged up with temp files
also check out the "auto defrag" it might be set to some silly time where it never gets to finish
your spec seems fine for what you do, a little bit of an "if it aint broke" situation
are you thinking of win7?, your system is well peppy enough to be a media system and general web/office use
I dont think you would see much of a day to day difference compared to the amount you would spend
good luck anyway
when upgrading its always a good idea to upgrade motherboard/ ram and processor all at once
especially since the nice new AM3 stuff takes ddr3 ram
you could just get a am2+ board and am3 processor on there but it would be limited to lower FSB speeds
Cheers
Bo