Desktop will not start up...safe mode will not load past mup.sys file??? Anyone know how I can fix this?

I have an ancient Dell Dimension 8400 desktop that has Windows XP 2005 Media Center Edition on it and it suddenly stopped working...when I turned the computer on it just sits at the Windows start up page and never advances...when I manually turn it off and try to restart in safe mode it shows a long list of files its loading but always stops at mup.sys...I have tried everything I can think of...I dont have a repair or recovery CD but I do have the OEM version of Windows XP which apparently is pointless...also like an idiot I have thousands of important pictures that I had yet to load to CD and losing them would be total devastation :~( Can anyone think of ANYTHING I might could do to fix this issue??? Please & thank you in advance!!!