boot off a windows 7 usb installation flash drive, and run startup recovery, and you can also try going to the command prompt from the installation usb, and run things like
bootrec /FixBoot
bootrec /ScanOs
bootrec /RebuildBcd
bootrec /FixMbr
those are windows 7's equivalent of xp's fixbr fixboot and bootcfg /rebuild. Win9X had just fdisk /mbr. With Win 7 it's one command bootrec with whatever switch.