Its possible that vista fixed the issue by software rendering direct3d instead of hardware. this will cause alot of overhead on your cpu. as it will then have to go through your cpu, then your gpu, then to your monitor. instead of straight to the hardware.

And it is impossible to run dual monitors on SLI. it wont let you so i doubt hes got them in SLI. as soon as you turn off sli you can use dual monitors again.