Most newer PCs have a fairly easy BIOS update procedure: Just download the .exe file from your PC manufacturer's Website, quit all open programs, run the .exe, and let it handle the patch; then reboot. If your PC suddenly shuts down in the middle of the BIOS update, you won't be able to boot up, so make sure you're not running off a laptop battery. Ideally, you're plugged into an uninterruptible power supply (UPS), especially if you're in an area prone to blackouts.
Older PCs, however, might require you to set up your own bootable disk to update the BIOS yourself. You might still be able to download an app that configures a USB thumb drive, blank CD/DVD, or even a floppy disk so that you can boot off of it to update the BIOS, or an ISO image file that can be used in your disc-burning app of choice (if you don't have such an app, try ISO Recorder for Windows XP
or the version for Windows 7/Vista
) to create a BIOS update CD.
Other systems will have you copy a few files to your bootable disk, restart, and open up the BIOS during startup (typically by pressing a specified key for setup options), and change the boot order so your system looks for a bootable USB drive or CD before loading the OS from your hard drive.