Warning: Screwing up a BIOS update can put your board in a non-functional irrecoverable state.
First identify the BIOS manufacturer. A quick google shows the VIA M9000 mainboard has an AWARD flash.
Then locate the BIOS update program released by the BIOS manufacturer - in this case google around for "AwardFlash".
Download the correct BIOS (usually *.BIN) for the board. Be very sure you have the right model and check the README that it can be used on your board revision.
Follow the instructions that should come packaged with the BIOS update program.
As a sidenote, there are utilities out there that would allow you to modify the BIOS file, providing access to undocumented features and offering new ways to mess up your mainboard.