I was hoping to upgrade it into a gaming PC, so I got the case I wanted and built an OK machine by my standards.
I built it using the following:

1) AMD 64 Athlon 3200+ (2.0 Ghz)
2) JETWAY Mobo with 939 CPU bus, 6 PCI slots, and 1 AGP slot (no PCI Express)
3) 1.5 Gigs of Rosewill PC400 RAM (3-piece)
4) Western Digital ATA, 7200 rpm, 250Gig harddrive (not SATA)
5) ATI Radeon 9550 256MB, AGP 8X graphics card
6) Sony DVD-RW Drive
7) Asus 'A'-Drive
8) Aspire Case w/ 370w power supply
9) Standard Silitek $4 keyboard
10) Razor Diamondback lazer gaming mouse
11) An OLD monitor from our original Packard Bell computer, if anyone remembers them...

That's it. It's actually not too much better than any standard computer. But that all cost me $750 nearly three years ago.
Also, I may be able to build the PC, but I have no idea how to overclock it without murdering it. I haven't tried, really.

Post-build Additions:
1) Hanns-G 19" Flat-Panel LCD Monitor
2) Netgear Wireless Router + Rangemax Tech.
3) HP Deskjet F380 Printer/Scanner/Copier
4) Xbox 360 Wired Controller (awesome for emulators :P)
5) Creative Instant Webcam
6) Wacom Bamboo FUN.

I just got the Wacom for christmas, so I'm still working on my digital art skillz. I'm updating a sketch I'm working on as I make more progress on it. I'm taking my time as it's my first real project on my Wacom.