Some of the newer motherboards will allow you to set the boot
order without entering BIOS setup, by tapping the F11 key during
POST.
If yours doesn't, tapping the DEL key when your PC starts will
get you into BIOS setup, but sometimes it's the F2 or other keys,
consult your system documentation.
Once there goto the Advanced BIOS Features page, or boot menu
[again depending on your BIOS], here you can select the order of
boot devices.
rgds
Li'l Roberto