[mlwjackson]

My homebuilt PC has been intermittantly booting. About 20% of the time, especially if it is the first boot of the day, it will boot flawlessly. The rest of the time the power supply fan comes on and I can feel heat from the PS, the C: spins up I do not see the keyboard LEDs flash and the monitor screen stays black. When it does this the CPU fan does not spin up.

Today, with the first attempt to boot the system made it to the boot screen and stopped with the error code "bad check sum error". I went into BIOS and just told it to set optimized defaults. It went ahead from there and booted.

So, I know that the mobo is capable of full functioning and all subcomponents work. What is the possibility that my CMOS battery is dying. Could that explain the reason it boots much better the first time each day but fails to or is less likely as the day goes on?

Are CMOS batteries specialty batteries or just run of the mill silver oxide batteries like the one that go in garage door remote openers?

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How old is the system?
Yes low battery can cause this issue. The battery is like this one:

[rshaffer61]

How old is the system?
Yes low battery can cause this issue. The battery is like this one:

[mlwjackson]

The system was built in October 2007.

[rshaffer61]

OK it's not the age per say but the battery could be the cause. I have seen batteries last years like mine which is 10 years old. Others I have seen start losing power in a couple of years.
It is worth a couple of dollars to just make sure.
Just realize you will most likely have to go back to the BIOS and reset the time and date and make sure all your drives are seen. Let me know what you find out.