So, What happens after we see the mup.sys driver load on a safe mode boot?
The windows OS is looking in the registry, executing PnP (Plug and pray) and ACPI routines checking the components and resources found.
It then starts these components possibly causing more draw on the power supply. Consider here the load of non-self-powered USB devices.
If there are any unrecoverable problems here, that will cause the system to hang and it will look the same. - The system hangs during a
safe mode boot after loading mup.sys!
The main reasons for this Windows XP or Win 2000 boot hang or alleged mup.sys issue are:
* Hard disk failure or corruption
* A corrupted registry or registry hive
* New hardware has been installed but not did not completely "Register or re-Register" correctly
* New hardware has been installed but it is faulty or failing
* The new hardware's driver or windows itself has been compromised (Disk data corruption or by a virus) or (rare) needs to be updated
* The power supply is marginal in output or failing (Common per user feedback)
* BIOS\ESCD\Motherboard chipset driver conflict with a component, its driver, or its registry data
* Existing hardware including the motherboard may have failed in a specific way but not catastrophically.
In my experience, I have never found that the mup.sys driver is actually the cause of the problem but replacing it with a known good uninfected version
won't hurt if just to exclude that possibility. Also, disabling the mup.sys driver by using the recovery console normally does not help either. Windows will
then just hang at the driver that loads prior to mup.sys.
From here:
http://www.aitechsolutions.net/mupdotsysXPhang.html
