Boot Select: Druing the boot up logo, press the key.
Dell/Alienware: F12
HP/Compaq: F9
Asus: ESC
Acer: Go to bios MAIN to enable F12
Lenovo: F12 or FN+F2
Thinkpad-Lenovo: F12
Sony: ASSIST key / F11
Samsung: F10 - boot select.
Toshiba: F12, also can enter bios
Gateway: F12

If you need to boot to "DOS" using a USB device, enter the BIOS Setup, select the "Advanced" menu and set the "Fast BIOS Mode" item to "Disabled".

BIOS Key:
Dell/Alienware: F2
HP/Compaq: F10
Asus: F2
Acer: F2 or FN+2
Lenovo: F2 or FN+F2, may need to be enabled in BIOS first.
Thinkpad-Lenovo: F1
Sony: ASSIST key / F2
Samsung: F2
Gateway: F2

Diagnostic Key:
HP: F2
HP: F1 <= display system bios infomation, such as serial number.

Recover key:
Acer: Alt+F10
Asus: F9
Gigabyte: F9
HP: F3 or F11
Sony: F10
IBM/Lenovo: F11

Windows 7 Recovery Key
HP: F11 during reboot.