Can't boot back into Mac

I know this isn't exactly related to the category, but in the beginning it was. I recently received a MBP as a hand-me-down from my grandfather. I am a happy user of linux systems, so I ended up making a bootcamp partition on the newest update of Snow Leopard to install Ubuntu on (10.10 specifically). The installation went great and all, and I can access Ubuntu, but there were no choices on returning to my Mac partition.

I just decided to completely wipe everything and put Ubuntu on the whole drive in the hopes of being able to install Snow Leopard again, because I could not boot from either the Mac OS X install DVD that came with the computer, nor the Snow Leopard DVD it was upgraded with. I still cannot access either DVD to reinstall my mac.

I have also posted this on the ubuntuforums and tried most of the startup options available (a lot of them don't work). When holding down the option key for instance, I am confronted with a lock icon that needs a password (which my grandfather has apparently forgotten). So I cannot access bootable drives in that manner. I would just really like to my Snow Leopard back up and running on this computer.

Please help.