It sounds like you may have deleted your Windows 7 partition. Did you pay attention to what was going on during the partitioning step of the installation process? Did it tell you it was going to use the entire disk for your BackTrack partition?
If BackTrack was installed alongside Windows (in a dual boot configuration) then you should be able to boot into Windows using a startup option when the system starts. If you dont see Windows there as an option, then its probably been deleted. Use a Linux boot cd and check your partition table using gparted or fdisk to see if the Windows partition is still there.