Most computers have a defaut setup to boot on a DVD or USB mass-storage:
- Intel/AMD PCs:
- Just after reboot, the BIOS dispays information.
- You may then hit ESC or F2 key (or whatever key is displayed) to enter BIOS.
- Change your BIOS to allow booting on DVD or USB Mass-storage.
- The boot order may be DVD/USB and then disc.
- Intel MacOsX:
- In the finder settings, select boot icon. Choose "Boot using another operating system" and select the live DVD or the Live USB mass-storage.
Tips : if a USB memory stick is inserted before booting, pressing F8 to interrupt the usual boot process will bring up a dialog giving the option to boot from the USB stick after all :)