Read all what every one had said,change and upgrade power suply to a 450 w. costum made for this tower, video card to ATI ision Tek X 1650 pro , ram to 2g, so going to change th HD to 2 HDs. Now questions is "what is the fastest Intel CPU in can install in this old war hourse??
You'll have to give some more input on what you are really looking for. Currently, your post is not making a whole lotta sense.
Is this PCV 520 the same as PCV-RS520? (That's what I got from Googling this). If so, then it's a Pentium 4 processor (probably socket 478), in which case, you'll have to replace the motherboard if you are to install a new CPU.