you need to wait untill after the bios screen shows. the screen should go blank, then hold F8. That should work. Otherwise if you can get into the system, tell it to show the startup menu (it is under advanced options in system properties) if you cannot get into the system, wait for it to start loading, then hard-reboot (hold the power button) - it should come up with the option then.
Elitebook 8440p, i5 520, 8gb, Samsung 840 SSD
Old/Not Working/Dead Laptops:
T61 7661CC2, 4gb, Windows 7 x64, 240gb intel SSD, 500gb Ultrabay drive
Toshiba Portege 7020ct
Thinkpad T41 23737FU
Dell Latitude LS