I rebuilt an old pc for media pc use using old parts advertised here (thansk folks).
XP2600 Barton 2Ghz
2 gig ram (windows xp)
x8 agp gfx card 9550 bios as 9600 pro (Same board and chip)
Other stuff I can't remember!
Old M board.
Anyway it works fine for movies (Hi def 720 its fine but struggles for 1080i blue ray etc can hesitate a fraction)
I've noticed the security stuff has slowed it down but it's worth it. New security stuff is less intensive-even Norton jumped on the band wagon...
A friend had 256mg and 3gz processor so we just stuck in 2gb of ram and it's stopped crashing and surfs/office etc fine. Plays movies etc.
It does the best it can do now but even that is limited to the gfx and cpu being old.
Also old hard drives can slow down if the bearings are going-check for loud noises.-No rattles-then it should be ok.
Using a dual core processor-sure I noticed a difference when multi tasking but not that much and I don't play games on pc or engineering programmes except video editing that can use dual+ cores fly and on my old media unit takes ages-so I don't use it for that.
My laptop is a better spec that my media pc lol.
Besides wait for USB 3 to come out later this year and the Jan multi cores to come down a bit.
As above-crucial scanner.
I have a mac too-but I won't be the one that says buy that! lol.
£20 upgrade is a bargain to get more life from your pc then next year windows 7 and usb3 and cheaper quad cores-build a new pc if you need it.