I think we've a Compaq from 1999 or 2000, with an AMD K6-2 or K6-III. Shouldn't be clocked any faster than somewhere in the 500 MHz range, should have at best 128 MB RAM, a 20 GB (?) hard drive, and not much worth a mention otherwise.
My dad might still have my old HP Pavilion XL768, also from 2000, sitting somewhere in his house...had a more powerful setup with 900 MHz AMD Athlon, 128 MB RAM (upped to 256 MB around 2002), 60 GB Maxtor DiamondMax 22 (model 96147U8) hard drive, shipped with an nVidia Riva TNT card (upped to a Radeon 9000 Pro), with my first DVDRW drive (HP DVD Writer 530r/LiteOn SOHW-832S) and my second DVDRW drive (Sony DW-D22A/LiteOn SOHW-1633S)...though I also vaguely remember my LiteOn LTR-52327S being in that system as well. Added a Seagate 300 (200?) GB hard drive and had to fight with the overlay software to get the setup perfect. AMD northbridge, VIA southbridge, added in USB 2.0 via a PCI card with an NEC controller, and added fans with pretty blue lights. Motherboard manufactured by Asus, interestingly enough.
But the oldest I know still works -- because I have turned it on within the past two months -- is a 2005 Sony VAIO VGC-RB43. Well, mostly. I killed the motherboard with a bad flash, so it was replaced with an Intel D101GGC board, which cut the max RAM support in half (2 GB is the cap, as opposed to 4 GB, but I only ever had 1 GB RAM for it), switched me from ICH6 and 915G south/north combo to ATI Radeon Xpress 200 north/ATI SB400 south combo. Poor USB performance due to the southbride (apparently ULi produced a compatible southbridge with much better USB 2.0 performance), and a much slower POST process than the original board. The SATA controller in the southbridge is just comprised of 2x Silicon Image SIL3112 (not bad, and performs well with the one SATA optical drive I have), and the PATA ports are stable enough. Realtek audio, Realtek NIC, no RAID, no support for FireWire (original Sony/Intel board had Firewire by Lucent/Agere/LSI I believe).
Added a Radeon X1300 Pro to the VAIO, but took it out shortly after the ball bearings began to annoy me. Original HDD in it is a Samsung SP2004C at 200 GB, 7200RPM, SATA 1.5Gb/s. Added a Seagate ST...uh... well, it's a 320 GB model, 7200 RPM, SATA 3.0Gb/s maybe, Barracuda 7200.7(?); then later added a Western Digital Green 500 GB model. (So I magically had 1 TB of storage by 2008 or so). Current ODD are LiteOn LH-20A1P and Optiarc AD-7201S (the latter pulled from an HP system).
Never did quite rig the front LEDs up to the motherboard properly in that VAIO....:doh: