I always get the message about SLI being disabled, its annoying as **** but you just click the little cross and forget about it until you next load your machine.
As to the crashing, try uninstalling the graphics card driver completely (using Driver Cleaner after the uninstall), and then reinstalling the latest nVidia driver cleanly. If it still crashes then rollback to an earlier Forceware driver that worked, and then try out different drivers for your other hardware (motherboard, sound card, etc.) and then try the video driver again.
AMD 64 X2 4200+ @ 2.2ghz
2048mb Corsair PC3200 RAM (2x1gb)
WinFast NF4SK8AA Motherboard
660GB HDD Capacity (3xHDD)
600w Enermax PSU
eVga 8800 GTS 320mb