I had some employees with recent mup.sys problems, and after fixing it, I found that other people posted a similar problem here a couple of months ago, but there wasn't a real complete answer. http://www.computing.net/windows2000/wwwboard/forum/37902.html In case anyone's still having hang problems with Mup.sys after doing hardware upgrades: There are a few situations which can cause Mup.sys to hang. Major hardware changes are the most commom, particularly motherboard changes. A lot of times the effect is hidden until you install other devices after a motherboard upgrade. First thing to check is the BIOS settings, make sure you are set for a PnP (Plug and Pray) OS, and that IRQ's are managed by ESCD. If you have non-PnP OS set, or if IRQ management is set to manual, and you have a device sharing an IRQ with your modem (if you dialup) or your network adapter (if you're on a LAN), Mup.sys will often cause a hang when it's loaded, because it tries to access your network connections and will cause an IRQ conflict with the other device. PnP and ESCD management of IRQ's lets different devices share IRQ's without hanging. In the last ten days, I've seen three different cases where systems got Mupped - one directly after a motherboard upgrade, and two some time after a motherboard upgrade, but immediately after other hardware changes. In all three cases, the problem was solved by: removing the new devices and going back to original hardware; starting XP in safe mode, (to clear the new devices from the device manager hardware list); then shutting down, making the BIOS changes on reboot (immediately after installing the motherboard in the one case where that was the problem) then starting up normally, finally, reinstalling the devices. The reason Win9x doesn't have this "problem" is simple - Mup is an NT item. Hope this helps.

Thanks for this info!

From my viewpoint, the major reason for this difference between XP and 98 is that it is part of the Microsoft Anti-Piracy features in XP. XP is tuned to recognise significant changes to its environment and refuse to BOOT, for example a change in Motherboard as you have evidenced. For those who have attempted to GHOST a running Windows XP config from one PC's Hard Disk and then load a GHOSTED disk into a second PC which is significantly different, then XP fails to run. It then takes a restore, reinstall or other activity which will required the XP CD-ROM. Not necessarily available to the user of a 'pirated' operating environment.