Find another computer with similar - better specs that needs a HD, and stick the HD in it, and take the old thing to a recycle bin, and toss it in.
Well, this is rather fast, being 2.8ghz and tweaked. The main advantage is that 64 bit can take more ram, as i use of most 3gb even in XP.
I did see these as offering the best buys. What do you think:
http://www.computerlx.com/view_cart.aspx
http://www.pricewatch.com/gallery/computer_systems_with_os/phenom_555
http://www.pricewatch.com/computer_systems_with_os/
http://www.pricewatch.com/gallery/computer_systems_with_os/athlon_ii_x4_640