If you have a thumb drive you can make that bootable and run fdisk off of that. Here is a link on how to do that.
http://techpaul.wordpress.com/2007/06/28/put-your-thumb-drive-to-work/
As for flashing the BIOS you have to find out what manufacturer the BIOS or go to the computer manufacturer's website, or go to the motherboard manufacturer's website. Either way they should tell you how to flash the BIOS specific to your computer.