Would a bad CMOS battery effect my O/S? My computer periodically reboots for no reason at all.

There are literaly dozens of reasons, both hardware and software for a PC to reboot itself, but I don't believe a CMOS battery could be the cause. Did you change/add anything just before this started?

I agree with raincheck, the CMOS battery would not cause a re-boot. Once a computer is up and running, the CMOS battery plays no further part in the proceedings. Again, there are many causes for a re-boot but one of the most common causes I have found is a dodgy power supply. If you have added anything recently it may be that you are pushing the power supply beyonds it cababilities. On the other hand it may be that the power supply is just not up to the job in the first palce. Try checking with a known good power supply. Stuart

When my computer reboots it gives me an error message that says "your computer has recovered from a serious error" (or something close to that). I've looked at the error report and it said that it was caused by an unknown driver. I recently changed by isp and went from dsl to cable. When I installed the driver for the linksys cable modem it hollered that it wasn't digitally signed. I did however call Linksys and the gentleman that helped me assured me that it was a Microsoft quirk they added to XP and it shouldn't effect the performance of the system.