Unplugging/plugging in the floppy power while the machine is on shouldn't cause any damage unless you shorted something out in which case the PSU should've turned off anyway. I've unplugged/replugged floppy drives many times already (when realigning them) and haven't had this problem once. It might just be a coincidence or a bad static discharge. You rebooted, or the machine rebooted itself after you plugged it in? The latter indicates that you did indeed short something out.Remove the CMOS battery, unplug the power to the system, wait 30 minutes, then replace the CMOS battery and restore power.