It has been pointed out to me that if it was a CMOS battery problem, the date and time would be out. It has been suggested that the problem could be failure of the hard disk to run up. I do not have a disk diagnostics for this PC so I have to take the top off to read the label. I have not taken the top off this PC before. 4 screws secure the side plates to the back plate. however, these side plates are also held in by the top plate and that is riveted to the back plate. I know I am missing something simple. I would welcome becoming informed!