I was installing Vista from a DVD under VMware and needed to the change the boot order in the BIOS to boot from the optical drive first.  The problem was the BIOS splash screen went by so fast I couldn’t hit the F2 key in time.  I found the solution by adding a line to the VMX file of the VM:

bios.bootDelay = “boot delay in milliseconds”
15000 gives you 15 seconds to hit F2.  Alternatively, you can add:
bios.forceSetupOnce = "TRUE"
to automatically enter the BIOS at the next boot.