I have intel dual core processor,4 gb of ram,ATI 6770 hd graphics card and windows 8 64 bit OS. When I leave my computer for a while(I mean not making any movement by mouse or keyboard) a blue screen flashes and it shows "YOUR COMPUTER RAN INTO AN ERROR" and then restarts and after restarting it can't detect my Hard Disk.This problem didn't occur at beginning when I installed Windows 8 but I didn't use my PC for about 6 months and when I started using it again this problem occurred.I installed latest windows updates but the results are still the same.Another one, when I open task manager it shows disk usage 100% and my PC is running slower than usual I closed every application running in background but it didn't change anything.
It could be that, one is failing.....
You can try to disconnect both HDDs.
Then connect one HDD and boot into bios to check what it shows. If the right things turn up.
Cycle the HDDs and see which one is giving way.