When your computer turns on press either Delete Key or
the F1 key this will be shown on screen as press to enter
set up.
Once you get the Bios screen you can then go into the
boot menu and change the first boot location to cd rom,
best bet is to change them all to CD then change it back
later.
Remember once you format and load windows again after the
first reboot, always say boot from hard drive it will
give you the option on screen.