I will be using my computer and the, for no reason at all, the computer will close down and I get a screen telling me there is no operating system installed, So I go into the Bios and the main hard drive has disappeared. If I then swap the SATA drives around, the drive will re-appear and, after placing it is the main boot drive, the machine will re-open. I have no idea why this is happening but it is starting to get on my nerves now Anyone have any ideas about what might be causing this? I'd be so greatful.