No icons-mup.sys hang-no task mngr

I have researched many, many forums but cannot fix this:
Running XP Media Center Edition on older Dell. When getting on system, it gets to the welcome screen, but when I click to get in, it goes in, then signs off quickly and goes back to the welcome screen. In safe mode, it stops for a long time at mup.sys, the goes on the the same result. In using the provided disk, it goes to the screen saver, but there are no icons, no toolbars, cannot get to task manager, nothing. I've tried many fixes, hive fixes, etc.. and there is no indication of power problems, disc problems, etc... likely a virus/registry problem. So advice of running any software to fix cannot be done. The posts I have seen are several years old, but I am wondering if there have been any latest answers. A tough one...thanks.