to enter the BIOS during boot up hold down one of the following keys:
Hold down the <Del> key
Hold down the <F1> key
Hold down the <F10> key
To enter the BIOS from a DOS prompt...( ...NOT from inside windows)
<Alt><Cntrl><Esc>
<Alt><Cntrl><Enter>
<Cntrl> <Alt> <A>
<Cntrl> <Alt> <S>
Some manufacturers have their own way for entering BIOS as shown below...
Acer - Ctrl+Alt+Esc
Compaq - F10
Compaq Presario - Press <Alt> <Ctrl> <Esc> at boot when you see the "Compaq" log in big letters
Dell - F1 or Del.
Gateway 2000 - F1
Hewlett Packard - F1
IBM
Older Models - In order to get into the configuration of the IBM setup screen (CMOS) screen you need to hold down both mouse buttons during boot-up.
Aptiva - Press F1
Leading Edge
Fortiva 5000 - <Cntrl> <Alt> <A> or <Cntrl> <Alt> <S>
NEC - F2
Packard Bell - F1 or F2
Sharp Laptop 9020 - F2
Sony - F3, then F2, or F1
Tandon computers - Hold down the <Esc> key after turning on power
Toshiba Laptops - Toshiba Utility