fatal system error

A friend of mine has a blue screen with the message fatal system error this happened while trying to log on after doing a disk cleanup. My question is could she have removed something that caused this problem when she did disk clean up? She cannot log in to do a system restore. She does not know alot about her computer and had not ran disk clean up in about 10 months or ever did a defrag on her computer.

I read that disk clean up list things that have not been used in a while and this was the first time she had run disk cleanup in about 10 months.she  remembers there being a lot of  disk space that  was going to be freed up after the cleanup, but since she had not ran disk cleanup in a while she checked all the boxes and ran it. It was then that it said her computer was locked and eventually went to the fatal system error screen. She can not get to control panel or any where since she cannot log on. Her computer is still under a year old what should she do? 

Thank you, Cindy