If you cant get it to boot mostly either the computer is not set to boot from dvd first or the disk is not bootable or the optical drive's bad. You can vary each of these functions one by one to determine the cause. If you havent yet tried, tap F12 repeatedly at boot to invoke the one time boot menu and select the dvd drive there (that may or may not work).
Alternatively, get hold of a 4gig + flash drive, make it bootable with diskpart or ultraiso, dump the contents of the disk into it, set the computer to boot from usb first or manually select with F12, then install.