Windows 7: Infinite Loop to Sys Repair Screen, Trying to Reformat and Reinstall

Computer crashed, boots to system repair. Most of the time the system repair option, when pressed, loads files and returns to the same place. When it works correctly, I cannot access the advanced system restore options b/c none of my three passwords work with any of the three usernames listed. Possibly I just made a random one and forgot it, but that's beside the point... System will not boot in safe mode (c:/ or otherwise) and will not boot from an install disk (just the downloaded Windows 7 64-bit ISO) despite changing the boot priority to CDROM. I just want to reformat everything and start over but I cannot get to C:/. All my information is backed up so that's not an issue.
Perhaps hitting the hard drive with a hammer will cause it to reformat itself?