You should be able to boot from the dvd provided you change the settings in your bios. To edit bios : just after switching on (have your monitor warmed up not to miss that !) push the 'del' key (that's 'del' for Award bioses but o.w. look for clues on the bottom of the screen).
Boot sequence is often on the 2nd page. Select cdrom first using PgUp/PgDown ; hd 2nd. Floppy : that's your call.
Quit and Save . (And take care not to change anything else if you don't know what it means ! ). And if you'd ever messed up you can always exit without saving changes.