I just got an error message when booting up. "System battery is dead-Replace and run setup". Two beeps. Then F1 to resume. or F2 to enter setup. F1 states "Operating system not found" F2 brings me to a screen that states "The CMOS checksum is invalid. Default values will be loaded" enter brings me into the BIOS where my system clock is "zeroed" out but running. I save the changes and get the same result. I changed the battery and also the same result. Any help would be appreciated. Thanks, Joe

What you've described are the classic symptoms of a flat cmos battery. I would replace it under those circumstances. You're not clear as to whether you have setup the date and time and also the harddrive parameters and then saved since you have replaced the battery. Assuming that you didn't overlook this basic step (we all do it sometimes) it is time to check the battery. It may be old and already no good. You may have overhandled it, touching both sides of a silver oxide battery can discharge it in as little as five minutes. If you have access to a volt meter, check that it is within specs. Also check that you haven't installed it incorrectly. It's also possible that your motherboard has developed a fault.

Some motherboards require that you leave the battery out for a couple of hours. I have a Hewlett Packard Pavilion DeskTop which I had the same problems and had to leave the new battery out for over night before it would work.

Make sure that you didn't install the new battery upside down.

I changed the battery and had no luck. Maybe it's the MB which is more than I can handle. Thanks for the advise anyway.