I will take a stab at saying the MBR sector is toast, as you say the fixmbr / fixboot was not recognised
new HDD, once you get this sorted
but as HDD - in my scenario - is bolloxed, you may need to grab a SATA to IDE converter plug, it just plugs into SATA drive
and makes it IDE
then slave it to grab data
MS update had that one feck up a while back
you had to remove the old update to clear fault
but again, everything you have posted points to a fecked drive
probably a coincidence the PC fell over then
but worth checking once data is secured

then, as Info Au said, partition your drives before you ever use PC