The clock on my PC (yep, bottom right-hand corner) has very recently started to show the incorrect date and time. For example, earlier today when I booted it up, the clock showed something like 13/10/2012, 21:54, when actually it was 14/10/2012, 11:01 (roughly, you get the idea).

Could it be a flat CMOS battery as my PC is now 4 years old? Or is there something in the BIOS I could or should check? Also, if you change the CMOS battery, do you lose the BIOS settings?

Any help gratefully accepted.