I built a PC that's been working for a while (aside: mainly using a non-Windows OS, which seemed to start kernel panicing more frequently). It stopped booting in any OS from the partitions on the SSD (giving BSOD 'STOP: 0x0000007B (0x80786A58, 0xC0000034, 0x00000000, 0x00000000)').
I installed Windows 7 on a separate drive and magicandre1981 kindly explained how to make the old SSD partition work by switching to AHCI mode in BIOS (and make the new HD partition work by enabling AHCI).
However since this whenever I select shutdown in either Win 7 partition, the machine restarts instead (it shuts down in 1 out of 10 attempts). This happens even when I explicitly log out and then shut down from the logon screen, and even with all cables bar power & monitor unplugged. This SU question suggests updating to BIOS, but I'm not sure other OSes I want to reinstall/reenable will work after this. I'm no BIOS expert, but have changed a few relevant-seeming settings, and mine look much like the bottom half of these ones.