Here is possible list of Keys:
AMI (American Megatrends) - AMIBIOS, AMI BIOS
Press Del when after powering on the computer. Some older motherboards
that use AMIBIOS may prompt for the F1 or F2 key instead.
AwardBIOS, Award BIOS
Press the Del key to enter the BIOS Setup Utility on nearly all
AwardBIOS powered motherboards. Some older systems using Award's BIOS
software asked for Ctrl+Alt+Esc to enter BIOS.
Press the Esc key to enter BIOS, right after powering on the PC.
Microid Research -
Press F1 to access the BIOS setup utility.
Press Del during the Power On Self Test, immediately after the
computer starts. Many older Phoenix BIOS systems required
Ctrl+Alt+Esc, Ctrl+Alt+Ins, or Ctrl+Alt+S to access BIOS. If you're
still having troubles entering BIOS or can't figure out what company
supplied the BIOS on your motherboard, here are some keyboard commands
you might want to randomly try in addition to the any of the ones
F3 F4 F10 F12 Tab Ctrl+Alt+F3 *Ctrl+Alt+Del Ctrl+Alt+Shift+Del* (using
Del from the keypad) Ctrl+Insert *Ctrl+Shift+Esc* Fn+[any "F" function
key] (on some laptops)
Check if BIOS reacts to your keyboard at all if you have USB keyboard.
If it doesn't react to USB you do not have USB support enabled in BIOS and you will have to connect PS2 Keyboard
To enable BIOS suppor for USB devices follow this tutorial.