Though a failed BIOS update doesn't endanger the data on your hard drive directly, you will be able to access your files and continue working with them on another PC or Laptop without delay if you have a backup on a removable drive.
Similarly, creating a backup of your BIOS is also a good idea.
In most cases, nothing will go wrong at all, but it's important to know that there's an associated risk and not to treat the process too lightly.
Typically you won't need to as a PC or laptop will be set up to look for a removable disc or drive before trying to boot from the hard drive.
Alternatively, look for a 'Press F10 for boot options' or similar as your computer is starting to bring up a list of drives.
To make a USB drive bootable, you will need a utility such as Rufus or Unetbootin.
Head to the motherboard or laptop manufacturer's website and look for a support link.
You should be able to search for the model and see a list of available downloads, which might include manuals, drivers and BIOS files.
Additionally, the full model name –such as P5E3 Deluxe – is usually found somewhere on the board itself.