Not a question - an answer. I discovered this while trying to "downgrade" an Acer PC to Windows XP.
I kept getting a stop 0x7B with a message indicating that the hard disk may have been infected, or corrupted.
Final resolution turned out to be that the DVD drive in the PC had no "DOS" driver that the install routine could call, and so past the point where XP install would say "Starting Windows" the system would crash with the 7B error. This was an LG Electronics OEM drive. LG Electronics techs were very helpful in providing this information.
Solution was to use a retail CD (or DVD) drive which DID have drivers. Then the XP installation was successful.