At least the chip supports it. http://www.lsi.com/n...ducts/fw_322_323/
The HP page doesn't give much info on the PCI slots - http://h18000.www1.h...%20Specifications
The peripherals are PCI 2.2 and PCI 2.3 compliant. PCI 2.2 requires 3.3V rails. http://en.wikipedia..../Conventional_PCI Presumably there are no 5V rails in the PCI connectors, but the card should work (unless something else on it requires 5V and that seems unlikely).
Unfortunately, since it's an HP/Compaq, it can be hard to find troubleshooting information.
I haven't been able to find much of anything else useful, except for scattered reports of others having trouble with the same card.
Good luck.
Cheers,
Scott.