If you want to use PCI card look for `Fujitsu Siemens Futro S400`: https://www.parkytowers.me.uk/thin/Futro/s400/
It has the same CPU and chipset as HP T5720 (tested by Phil) but it is IMO a better choice because:
* Case is big enough to install one of these chinese GeForce FX5500 PCI
* You can install CF card inside, additional adapters are not needed (16 GB Sandisk card didn't work for me, but 4 GB Transcend was fine)
CPU performance is on level with P3 or Athlon 1100, so it should be more than enough for games released till 2002/3.
Pentium 4 2400 + ASUS P4C800-E Deluxe + 2 GB RAM + GF FX5700 128 MB AGP + SB Audigy + Tagan TG330-U01 + Win XP SP2
Duron 1000 + Soltek SL-75DRV4 + 256 MB RAM + Voodoo 3 2000 16 MB AGP + FM801 + FSP 400-60PFN + Win 98SE