Motherboard manufacturers, such as Asus and MSI, have live BIOS updates. You download the software for live updates, install it, and run it while online.
The BIOS update is dowloaded and then installed when the PC is restarted or is next booted.
I have done it with two PCs with MSI motherboards with no problems.
Just remember that if there is no pressing need to update the BIOS don't do it. Only do it if it's to fix a bug or add support for hardware.
What is the make/model of your PC's motherboard?