Hello, I hate to tell you this but your windows installation might very well be gone. This has happened to me as well when i installed backtrack to the hardrive and tried to dual boot it. One thing you can try is to boot up to backtrack via bootdrive and then access your windows partition and try to transfer the data to an external hardrive that is what i had to do.
good luck with this let us know how it turned out.
Cheers !


