I searched this site for other mup.sys stuff, but it seems that a lot of people's experiences are unique, but still in some ways the same, so I thought I would post mine in the hopes of getting some insight.
If there is a power interruption (like the electricity gets cut off by a storm) or the computer is shut down and the power cord removed (in anticipation of the electricty being cut off by a storm!), I cannot boot the computer past mup.sys when I turn it on next. I can't boot into any safe mode option, and pressing F8 and going from those options doesn't work either. I always get the load up screen, then the keyboard flashes all three of its lights, the harddrive light turns off, and it hangs. I noticed that while trying to boot into safe mode that mup.sys is the last to show, but the harddrive light is still flashing for a few seconds more before the hang, so I figure it's not actually mup.sys at all.
After rebooting the machine about a dozen times, both with the reset button and the on/off switch, I put in my XP Pro disk and try to boot off of that, after fiddling with the CMOS settings. I don't ever get the repair option. Instead, it starts loading everything for setup, and then it says "Loading Windows" ... and hangs. The harddrive light turns off, the keyboard flashes its lights, and the CD ROM drive light turns off too.
I have two harddrives installed, and have tried to boot off both. The slave drive always experiences hardware failure at that point and doesn't go anywhere, though it does work when the other drive is up and running.
So then I repeatedly reboot, plead with the computer, tell it it sucks, beg it to work, tell it I love it, hug it, walk away before I kick it, sulk, sigh at it, pat it, then finally tell it "Fine, be that way!" and go to bed.
This morning, after being down for about 36 hours, it inexplicably booted up. Everything works, and works just the way it did before. This is what always happens, in each of the three times I have had this problem. Usually, though, it works after about 24 hours. Then I get a bunch of pop ups telling me that Windows has recovered from some serious errors.
I would like to know how to stop this from happening, or how to fix it or use the CD to boot up, because it IS stressful, and I do miss being online when it happens, though I have to say that I did enjoy reading three novels during the downtime.