I really do not think Win 7 would kill your computer. If it is really bad, maybe something just got stressed out.
Could it be in hibernation?
Try unplugging it for a few minutes. Some folks suggest holding in the power switch for about 30 seconds while it is unplugged. I think this is supposed to clear the bios.
I lost one of mine the other day when I was plugging in SATA drives with it shut down. I thought that would be safe, but apparently not. I now turn off the power supply power switch to work on anything.