Originally Posted by CaroMark

I recently had a problem with my laptop intermittently shutting down. Sometimes it would run for hours but at other times when I would use it more it would shutdown. I went through all of the steps you detailed until a tech friend mentioned heat. I have since elevated the laptop to allow it to cool more and it has run fine. At this point I believe that it is one or more of the cooling fans that need to be replaced.

Good luck with your situation, hope the info helps.