UPDATE: bought a new copy of 64bit Win7 installer.
boot on disc, and tried the following:
startup repair: unsuccessful
fixmbr: "The system cannot find the drive specified"
fixboot: "The system cannot find the drive specified"
diskpart> list disk: "There are no fixed disks to show."
bootsect /ntf60 all: Successful
naunsa naman ni?? guba ang HDD kay dili madetect?