A few days ago, Jamie and I replaced some lighting fixtures throughout the house, which involved cutting power a few times. My computer was on while the power was cut, but that's never hurt it during outages in the past so I thought nothing of it...
Last night, I noticed that something I was trying to do was being incredibly slow, then I noticed the Diskeeper icon in the system tray and my hard drive activity light in its constant on state... So I right-clicked the icon and told it to suspent the current job for an hour, and the slowness ceased. That's weird though, because the background defragmentation is supposed to have super-low priority and not interfere while I'm using the computer, which it never had before.
Well this morning it started doing the same thing. So I thought, alright, maybe it just needs a reboot.
But it wouldn't.
I'd see the XP splash screen and its progress bar would get 2/3 of the way across, then it would reboot itself. Constant loop.
Ok, so I thought I'd try the Last Known Good Configuration option. But it does the same thing. Huh?
Then I tried Safe Mode. It shows the drivers it's loading, gets to mup.sys and stops for 10 seconds, then reboots itself.
I tried Safe Mode with Command Prompt. Same thing.
So then I used Jamie's computer to Google mup.sys and figure out what it is, since that's my only clue at this point. Woah. Tons of hits. Apparently that's because if there's anything wrong that prevents the GUI from coming up, it will look like mup.sys was the problem just because that's the last driver to load.
Great. Well, fortunately in one of the responses to a thread on Experts-Exchange, someone described the exact problem I was seeing and how he tried all the other things everyone else had suggested, like moving RAM to other slots, removing PCI cards, changing ACPI settings in the BIOS, and unplugging USB devices after mup.sys loads, and none of those things worked for him.
So the next thing he tried was to reinstall Windows, but it gave him some error about an update already being in progress or something and he ended up in the Recovery Console, where he ran a chkdsk /p and then used the "fixboot" command. After that, Windows booted up as if nothing had ever happened.
Ok, so I thought I'd give it a try. But first, what the heck is this fixboot command? And what does the /p option to on chkdsk? So I looked those up on Microsoft Support and they both turned out to be feature only available in the Recovery Console. They seemed safe enough to run without risking permanent loss of my data... I wanted to make sure I could still slave the drive to a new installation of Windows to get the data off it.
Well I ran the chkdsk and that said it found some errors on the drive. But I remember the last time I told chkdsk to fix the errors it found, and it caused all sorts of problems, so I decided to hold off on that and just run the fixboot command. So I did that, and in its feedback while it ran it said the boot sector was corrupted. Then it said a few more things, and then stated that the new boot sector had been written. Woah.
So then I rebooted and Windows loaded like nothing had ever happened. But now I know that there is a command called "fixboot" that apparently does exactly what its name implies. Interesting. Is this a Microsoft product? Seriously...
The question still remains... how did my boot sector get corrupted? My only thought is the power events, which is why I mentioned it, but it still seems unlikely to me.