Hello I'm trying to crossfire my Asus HD 2900 XT with a Sapphire 2900 Pro I'm wanting to buy from a friend, but it seems I'm having some issues with my system locking up.

My original system configuration:
OS: 32-bit XP SP3
5 Hard drives, 2 500 gb sata II, 3 80 gig with one 80 gig sata
CPU: Windsor Core, AMD64 FX-62 Dual Core
RAM: 4 Gig OCZ Crossfire gaming RAM
Video: Asus HD 2900 XT
Mainboard: MSI K9A Plat, Rev 1.0 running on the original BIOS and the board has PCI-E 1.0 slots and 580X chipset.
Other: Lite-On Sata II Dvd burner
PSU: Rosewood 850 watts

My system is not overclocked at all.

Here's my problem:

Whenever I try to hookup the 2900 Pro, the system boots up and goes into XP fine, but at some point it locks up. It does this even if the Pro is by itself, in either PCI-E slot. However, the computer is fine if I go back to just using the 2900 XT in either PCI-E slot. So from this I've determined it has something to do with his card, and none of my slots are bad. He was using this card in his own computer yesterday and he has the same power supply brand and same wattage. He was playing TF2 on Steam, and the card was working fine. My friend then took the card out and put it in a completely different computer that another friend owns and the 2900 Pro worked fine, no system lockups.

Now from what I understand with Crossfire, as long as they're from the same series, they're supposed by crossfirable and the higher card should match the lower card's clockspeed. Does anybody have any idea what's going on with this setup?

Even after resetting my motherboard bios back to fail safe defaults in case something I messed with might've been causing problems, it still locks up as long as that 2900 Pro is in there, either with the 2900 XT or by itself.

The only other thing I think to mention is that when I booted into Safemode [plus networking] with both cards installed, the computer didn't lock up. Before I ever attempted to Crossfire, I uninstalled the old display drivers and used Driver Cleaner to remove any traces of them from the system and got the latest from ATI. I don't have any more time at the moment to try anything else, but would manually setting the XT to match the Pro's clockspeeds do anything?

Thanks in advance.