I had exact same problem (stall at MUP.SYS) after upgrading my existing 3.x to build 4560.
I had an auto-login non-admin user with no password set to auto-login at startup.
I had another user, an admin, set up as another user.
After starting the computer after updating Parallels I was thinking that my user setup wasn't letting the Parallels upgrade complete, but since it stalled at such an early point I don't think that's what the trouble was.
Anyhow, using the Windows repair technique described above solved my problem. It was frustrating that it took about 45 minutes to complete the process but indeed it did work.
[edit] I was wrong about 45 minutes. It's now 1hr 15 min's and I'm stuck in update hell. Many reboots, Live OneCare then downloads updates, then reboot. Repeat many times. I'll get there eventually but it could be a very long haul if I've backed up to starting from the base SP2 that was on the CD.
Yup. Looks like I'm all the way back to base SP2. ("Installing update 1 of 72" and that's only on 1 of the reboots)
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Thank you for posting the solution.
Last edited: Jul 22, 2007