HIS Radeon HD 4890 secound gpu

i have a 2 HIS Radeon HD 4890 cards / and i have 1 of them in now . .
but when i put in the 2nd one it wont boot . .it gets to the windows start part but just when its ment to come on it Blue Screen . . ..
dont know wot to do . . i tryed everything . . im about to but a while different comp . .

My mother board is gigabyte x58-extreme
things that ive tryed is --
updateing my mother board but still doin it ..
formatted comp . it worked with both but when i go to update drivers it bluescreen
right when it finishes .
do know wot to try . im up for any help . .{Plz )
thankyou
Shmik .

 

is your psu powerfull enough to power both of them?
any way start up in safe mode as i t sounds like it bsod's when the rivers are implimented for 3d.
so try booting safe mode uninstall drivers restart in normal mode then re install.

 

If possible, I'd suggest getting a 5800 or 6900 series card. It should give about the same performance (and a lot of new features) on half the power. You should be able to pick one up relatively inexpensively these days.