by any chance where you upgrading the BIOS when all this started?
you can try this:
have you tried the F8 restore?
The instructions are very misleading. The F8 restore function is actually a Windows 7 function, not a dell operation.
The instruction book says to press F8 when the dell screen is displayed - this is incorrect. You must press F8 just after the dell boot screen finishes, before Windows starts. You also have to do a Restart, not a resume as the F8 restore function is not available when just resuming from sleep / hibernation.