I would have suggested using a usb keyboard.

On my desktop PC, the usb keyboard isn't recognised on boot-up. BUT if you do a soft reset (via windows) the computer recognises the keyboard and allows you to enter the bios.

They've told me they've tried a USB keyboard, but it doesn't "work" - in so much that it does once POST continues through to their present install of Windows - but not in the early-POST stages when their slamming the delete key to get into the BIOS.