What's up with my computer?

My desktop computer has recently been failing. It takes long to load up, doesn't load some programs, and when i boot in safe mode it hangs on 'Mup.sys' Is there any way to replace 'Mup.sys', will it solve the problem, or is something else wrong with it. I am considering re-installing Windows after i get my spare HDD back for transferring all the files i need on to.

Computer's specs are:

 

Yeah, the step I would do first though is to restore the computer to an earlier time. Use system restore to the date you know best that it worked great on. System restore has saved me so many times from shit that I was really deep into. Make sure you save important shit because system restore deletes some files, I think only changes registry shit but just to make sure because I know things can be corrupted by system restore.

If all else fails, and you can't find the specific problem just reinstall windows.

 

If you do system file checker it will fix that file

System File Checker:
Insert your installation CD, Start | Run | cmd | type "sfc /scannow"
What it does: Scans your computer for corrupted operating systems files and fixes them.

 

Thanks. I restored the system to sometime last month, all seems well at the moment, though i haven't tried to reboot it. If it still doesn't work I'll try wtp's way.

 

Could have been a virus or something.