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#11
The actual key to tap repeatedly to boot via the BIOS is often given on the first boot screen, and is never Enter.
Asus - F8
HP/Compaq - Esc
Sony - F2
Acer - F12
Gateway - F10
eMachnes - F10
Toshiba - F12
Dell - F12
IBM/Lenovo - the blue Thinkvantage button
If in doubt you can always ask here. You don't need to guess.