if it really did happen out of no where ( u didnt do somthin dumb like delete dll's, or system files, or see a virus deleting ur hard drive b4 it shut down)
Then it looks to me like a hardware problem. Did u build computer urself? I would check and make sure all connections are secure, and if u dont know much about computers you will have to take it to a tech shop for them to troubleshoot.
Worst case, ull have to re-install os, but if u have extra hard drive i would plug it up, see if it boots. That would tell u if it was hard drive or somthin else.
Just continue from there... called troubleshooting.