How are you trying to boot from the install disks
From the, restart to install, found on the mounted disk. Or are you holding down the option button at start up.
I would just insert the disk. Then restart your power book and hold down the option button. This should give you the option to boot from the install disk or your HD.
Are you sure these are retail, their not the grey system disks, are they.
If their badly scratched or dirty this could be a problem.