Some very old Sharp PCs require a Setup Diagnostics Disk to access BIOS.
Shuttle - Glamor G-Series, D'vo, Prima P2-Series, Workstation, X Mini XPC, Surveillance
Press F2 or Del on startup.
Sony - VAIO, PCG-Series, VGN-Series
Press F1, F2 or F3 after turning on the computer.
Toshiba - Portégé, Satellite, Tecra
Press F1 or Esc after powering on to access BIOS.
The following companies are either closed for business or no longer manufacture or support mainstream computers systems so verifying the following BIOS access information is nearly impossible. I have included what I could dig up for anyone who might be interested: ARI / ALR / AST (Advantage) - Press the Ctrl+Alt+Esc or Ctrl+Alt+Del keys. Cybermax - Press the Esc key. Tandon - Press the Ctrl+Shift+Esc keys.