Hi my XP Pro system got the mup.sys error just out of the blue today. Here's what I did: 1. Ran XP setup and logged onto my C:\windows 2. EXPANDed the d:\i386\mup.sy_ file to C:\windows\system32\drivers folder after a failed reboot or two I then followed the advice of whoever wrote about pulling out their mouse lead during safe mode boot. I was running a Logitech cordless mouse off that system at the time and I did the following to get XP to boot successfully: 1. made sure ACPI, Plug & Play, USB all enabled in BIOS 2. moved mouse from the ps/2 port to the first USB port 3. booted using safe mode 4. waited until it hung at Mup.sys 5. removed the mouse cable from the USB port 6. (3 seconds or so pass, the screen went black and safe mode appeared) 7. restarted system 8. booted normally into XP Pro job's a goodun', thanks to that poster! Thanks all Adam

Hi Adam, Many Thanx for letting us know it works!! It'll go into my archives so I can give people a link to this thread in the future! ___________________________________________ ☺ [Belgium, GMT+1]_________________________svg

i had a problem like this,windows would hang at mup.sys, and safe mod wouln't work i any flavor. but i didn't install any usb cards or anything. windows suddenly just started doing this. i tried loadins the recovery console from the win-xp boot disc, but thereit would spit out a disc error, but the cd was in perfect conditions, i tried booting off it from another machine and it worked great. i found out one of the memory slots in the motherboard was damaged. i changed it to one that worked and it worked fine.

My father's computer recently encountered this issue with the mup.sys, and his OS is a XP pro. It all started as a windows freez up while he was working on a Autocad drawing. When I restarted the computer, I got the options to load windows, so I chose Safe Mode and that's when I saw the process froze at mup.sys. I tried a few things from the forums on the net, but finally I suspected that a sector on the hard drive might be bad and interferes with the boot process. So I boot the computer from the XP CD and loaded the Recovery console, where at the prompt I typed chkdsk and hit enter. When the check disk operation completed the message said that a few hard disk errors were found and chkdsk utility fixed them automatically. I restarted the computer and BANG- windows XP loaded successfully. Hope this helps !!

I also had this problem and after much trouble it looks like it was hardware. I had an identical machine here and was able to swap the hard drive out to the other machine and it started working perfectly. Thanks! (Now I just need to see about fixing that other machine...hope its under warranty!)