My uncle has a computer that's about 18 months old, and there is a problem with his time and date. Every few days it resets itself to January 2003, and he gets problems with certificates because his computer thinks the certificates aren't yet valid, and also all his fax logs are messed up. Is this his CMOS battery failing? If so, are there different kinds of them, and how do I go about replacing it? Thanks, reps as usual.