If you still want to upgrade your BIOS, I'm assuming your board is the GA-EP45T-DS3R, please specify the full name next time.
Go here and download the BIOS update files:
Then use either unrar or 7z (7zip) on it to unrar the hidden rar file inside the exe. One of the files is called 'ep4tds3r.f3', that is what must be flashed to the BIOS. To do this, put it on a floppy disk and reboot. Gigabyte boards have a special feature where when you boot, go into the BIOS options and look for Q-flash, it's a small DOS implementation that will let you flash BIOS from your floppy drive. If that doesn't work get a FreeDOS floppy and use the provided 'FLASHSPI.EXE' to flash the BIOS. Be careful because you can brick you machine with a bad BIOS flash.