Nvidia sli problems

Heres the issue/question, Ive had my system for more that a year now which has had 2 duplicate Nvidia 8800's running prefectly in SLI mode with no problems.
However recently my hard drive crashed, which I've since replaced and reinstalled everything including the newest nvidia drivers.
The problem now is that my device manager only registers one video card and the nvidia control panel has no option to enable SLI anywhere. I havent touched/adjusted/changed the motherboard anywhere nor have I made any changes in the BIOS. What do I need to do to get back to where I was before my previous HDD crashed? Any help would be apprecieated. Thank you.

I never even touched the video card or the sli cable conecting the 2 card together, thats why im so confused as to what the problem is. But i will take your advise and give it a try. thank you