Can't start in safe mode(mup.sys)?

I've been to forums and searched here but can't seem to find the right solution to my problem. Here's the deal; whenever I turn on my notebook, windows xp is stuck at the loading screen with the blue bar moving over and over again. I tried to start it in safe mode, but it stops in mup.sys. However, I should note that in one of my first few attempts I WAS actually able to start safe mode(networking). I checked on attempt recovery and restarted, but was never able to get into any mode again. Is there any way I can fix it without having to do a format? The files in it are gravely important. I'd be terribly grateful if anyone can help me out.