The power supply died on my desktop pc (asus board with amd proc and windows xp home edition with sp3). Replaced power supply and eventually determined that even in safe mode it would boot as far as mup.sys then reboot. Running chkdsk from installation cd fixed it somewhat. It boots ok now and makes it to the desktop with mouse and keyboard working but: - no start menu or taskbar - wallpaper and desktop icons are present - during bootup several messages are displayed saying I don't have permission to change settings in catalyst control center (software for ati onboard video) - can access/edit/view desktop documents created with apps such as windows notepad, openoffice and google sketchup - can view saved .pdf files - can access and view desktop folders - cannot access files (mp3, mpeg) that use windows media player - nothing happens - cannot access desktop shortcuts to websites or a saved webpage on desktop (.htm or .mht). This results in error message "there was a problem sending the command to the program". internet explorer is the default browser - photo thumbnails appear ok but no viewer - can view/edit .jpgs with windows paint program - taskmanager runs ok and will run msconfig, sfc, etc. - it says Windows Explorer is running. Ending the task and restarting does not help - ran sfc - it ran for 30 or 40 minutes then ended without saying anything. Would replacing mup.sys by copying one from a known good system fix the problem? Could it be a registry problem or corrupt user profile? Any help would be appreciated. Thanks.