webral, I use HP AMD Phenom 9500 Quad core and had same problem some 6 months (??) back.
Eventually system fully crashed and I found out that the Hard drive was faulty (Sata). I used my laptop to search the sata website and sure enough the model I had was having issues and there was a an update that should have been actioned. Unfortunately normal windows updates do not attend to this.
Anyway I got replacement Sata HD under warrantee and also got my old hard drive back as I have a good mate (Computer Expert) who retrieved nearly all my old info from the hard drive. (phew)
May I also suggest that you have a back up system in place if you haven't already?
