I cannot comment about the need to pass a cheatcode for your particular box. As for pressing "shift" - you have to do this at the right time... At the very start of the boot process, just after your drive(s) have been detected and before seeing "verifying blah blah" You have to be fast, best to hold SHIFT as soon as your drive are detected, and keep it on until you see vmlinuz passing by, then you will see an entry stating "boot". Hope it helps, I have been sweating on this one many times, especially on fast systems...