If you have 2 of the same ATI videocards, or even a normal CrossFire combo, help me out... try this.
The more feedback I get on this, the more I'll look into it.
Go to ATI Support ( http://support.ati.com/ )
Search for "737-22378"
Click (and download / save) "To download this driver, please click here"
These are certified Catalyst v6.6 drivers with control panel that supposedly support crossfire across 2 X1900GTs.
Download CrossFireJack ( http://forums.techpowerup.com/showthread.php?t=15976 ).
Install the drivers (even if you don't have an nForce 4 Chipset).
Run CrossFireJack ... Enable CrossFire.
It's a hackjob, but it 'enables' CrossFire.
Don't honestly know for certain if it's enabled or if it's just faking it, it still looks like 6X at that small of a image...
Have fun with it.
Feel free to try it with other drivers too.
Requires .NET Framework 2.0 x86.