Shuttle Cases are awesome. Sure, they're trouble if you have a stack of expansion cards you can't bear to part with, and they're a spell toasty if you have a 7800 and an A64-FX2 in it, but you can't beat the form factor. And they're pretty stable/reliable.
P4 3.2Ghz (although it's only running at 2.8Ghz, and I can't figure out why.)
Can you fiddle with the multiplier settings in the BIOS config?
I, of course, don't have one. My current ride is an Athlon XP 2800+, Radeon 9500 (minspec for Oblivion!), 768MB of DDR333; all housed in a poorly-modified circa-1998 $40 steel case.
Viewport is a 19" Iiyama VisionMaster 450, a truly amazing CRT that is unfortunately showing signs of impending doom.
I also have an IBM (oldschool, in other words) Thinkpad T23, refurbished. 1.2Ghz PIII, 128mb RAM. Great for websurfing, typing, watching movies, running DosBox, etc. Minimalism is a virtue sometimes. And Thinkpads are rock solid. I've yet to experience any problems with it. Even ran a KANOTIX LiveCD just fine.
I would gladly upgrade if I didn't have to part with $1000 in the bargain. On the plus side, it's a nice excuse to get an XPC.