This article explains how to update the BIOS on a Legacy B3/C3 Rev.B

The Elo B3 and C3 Rev. B AIO touchcomputers were discontinued in 2016 and are no longer supported. The last BIOS firmware update that was compiled for these legacy products was version HC15V112. Please enter the system BIOS by tapping the DEL key on a connected keyboard and check the firmware version to see if you already have the latest. If you do not, you can follow the below steps to update to the last BIOS firmware created for these products.

Steps:
1. Create a bootable USB flash drive:How to create a bootable USB flash drive procedure
2. Download BIOS files and copy to the root of the USB flash drive.
3. Connect USB flash drive to the B3/C3 AIO and boot from it to install the BIOS firmware update.
4. When update is complete, remove the USB flash drive and reboot the B3/C3 AIO.