Boot up hangs on MUP.SYS file

My friend asked me to work on her computer. The other day her computer just wouldn’t boot up. She said she didn’t do anyhting, it was fine one night and then the next day nothing. I tried to boot into safe mode but it always hung up on the MUP.SYS file. She has XP Home but not the CD. I have XP pro but I cannot get to my recovery console to try and fix things. Any and all help would be greatly appreciated.