So here's the scoop:

 

The other day my brother was using my computer to type up a resume and in the middle of his work a blue screen appeared that said it was starting  a physical memory dump. He shut off my computer and when he turned it back on a blue screen came on and appeared to  be going through and deleting lines and lines of files in code. At the bottom it said the dump was complete or something like that.

                  When my desktop came up, everything I had in my computer was completely blown away -- it's like I have a factory fresh machine. Word is gone, all my icons are gone, everything is just gone. I assumed this was a virus because my computer had never done anything like this before, I've had it for 3 months. I did a virus check on completely updated Symantec AntiVirus and after 20 minutes of scanning a STOP blue screen appeared and it said a physical memory dump was completed (I guess there was nothing left to dump :)  I restarted my computer and it was dog slow--it took ten times longer to start than normal. My dad checked and saw that (after it finally loaded), the CPU was running at 100%--I have no idea what it was running and why it needed 100%.

                Anyway, the MY COMPUTER desktop icon (one of 3 that was left) was now gone as were the majority of the little icons by the time at the bottom right hand of the screen (I'm sorry I've forgotten what they're called.)  I ran a complete virus scan and it didn't show any virus or threats. I also ran a SpyWare scan and it showed nothing.  So what I'm wondering is, first, what caused the physical memory dump that dumped everything I had on my computer, and secondly, how can I fix this, especially if it really is some kind of virus. Thanks for your time and help.