When I turn on my computer it loads with the Dell screen and then before windows can load, it comes up with a black screen that says "Primary hard disk 0 not found" When I check bios it says that Primary hard disk is "unknown" However. I can start windows by just shutting off my computer and turning it back on again. This has been going on for a feew months. What is happening. I did nothing to my computer beforethis. It just started happening out of nowhere. Also....when it goes into sleep mode after the computer has been on for awhile....I can not get it out of sleep mode. I have to turn it off and start it up again.