External Harddrive ate my files

I am a rookie in Mac. I have a lot of multimedia which I store on external harddrives. Recently I have experienced my iMac freezing on me, specially when I am accessing the harddrives using my frontrow application. Eventually I got a database error when receiving mail to my Entourage. It was suggested that I repair permissions using the disk utility. This I did, however it never actually repairs anything, it just lists the stuff where the permissions differ. Anyway, straight after I 'repaired' permissions, my harddrive showed empty. No files left!!! 1TB data gone .

the way I understand it, it is a possibility that the file that lists the addresses of all the files on the disk may be the one that was wiped. I am hoping the data is still there and that someone has a nifty tool that will sniff it out for me.

All you great people with nifty tools, please help!!!