9600gt/SLI unrecognised(error 43)

Hi all

I know im new, but ill keep things brief.
I just got another asus EN9600gt to go with my leadtek PX9600GT on vista Home Premium 64x

For a while it worked (sli could be enabled, but NO difference in FPS/ 3dmarks). then i got new drivers and it screwed up and my second (the asus 1) got a error 43 in device drivers, after which SLI in NV control panel disapeared. I tried numerous drivers (mobo 20.8, NTUNe/nv system rools 1.6, GPU 179-181. everthing inbetween).

I just installed vista 32bit ultimate instead, Still the 2nd card comes up as error 43 and ntune refuses to detect it( aswell as rivatuner)
So, i switched the cards around, now the resolution cant change, BOTH cards have error 43 nvidia performance Control panel is blank, even with drivers.

Any ideas would be much appreciated

System specs:
Q6600/hyper212 stock
Asus P5N-D 0801 bios
2gb hyperx kingston DDR2 800mhz
stock leadtek 9600GT
stock Asus NX9600GT (new heatsink)
Armour+ MX
750W PSU
vista ultimate 32bit.