Shuts down by itself everyday at the same time

My friend could use some help. For the last few days, her computer has been shutting down by itself everyday between 5:30 and 6:00. She ran a virus scan and nothing appeared.

I asked her to run another virus scan, making sure it's the thorough scan, not just the quick scan, and to run Adware, Spybot, etc.. What do you recommend she does? Running XP.

Thank You!

 

Update,... may have just been some dust bunnies that decided to breed.
lol