Probably want to be more specific on the board. Asus makes about a dozen retail lga775 boards and probably some oems that aren't availible for retail.
Anyways, unless you missed some option in the bios, you are probably out of luck. While it is possible to rewrite parts or all of the bios, and someone might have released a hacked bios, this is generally only done for more popular, enthusiast boards as it takes a good amount of time and someone who actually knows what they are doing.
You could try searching for different bios revisions for your board but I doubt that you will find anything. It will be alot easier to just buy a new board or give up on overclocking your system.
just a side note, the bios is stored in a flash rom chip, not the battery.