So I was playing around with my 'unknown P4 network storage' PC last night. Turned out I called it NETBOX, and hasn't been turned on since Nov 08-ish. Go figure.
NETBOX is a P4 Northwood (3.0Ghz), and on idle it was running about 80ºC. A tad too hot. So I turned the machine off, removed the power cable, and took some cotton buds/Q-tips to the stock Intel cooler. They removed more dust bunnies than you can shake a stick at. I even blasted it a while with my Delta fan, which pushes air at ~200 cubic feet per minute, to get rid of the dust.
After dust removal, the CPU was a nice and happy 58ºC idle. Fantastic.
Some basic and quick overclocking resulted in stable at 3.52Ghz, somewhat stable at 3.6Ghz (enough for PiFast and SuperPi 1M), and a bit picky at 3.7Ghz. The RAM is 0.5GB of the generic DDR, unwilling to be pushed over 400MHz or above 250FSB. Most of the benchies I'll do at 3.52Ghz then.
The Graphics card in it is indeed a Radeon 9800, though with its tendency to overheat (even with the delta fan on it), I doubt it'll get through the tests :S