Friend going from Mac, to Windows, to Linux, and back to Mac.....

So, I have been a PC guy for a while now. I stopped using Macs about 5 years ago and have delved deeply into the PC world. However, a friend of mine is having a huge issue with her MacBook Pro (model A1212) and ended up doing far more OS jumping than is necessary. She's currently running an older Ubuntu make after having been on Windows for a bit on this particular device. I have a disc that I can use to run Mac OSX (made her buy one for her own sake), but I haven't the foggiest on how to boot from disc on a Mac, let alone Ubuntu. It retains the vintage Mac opening gray, but from there I have no idea what to do. I've tried left option for booting, I've tried f8, and I've tried f6 on startup to no avail. Any suggestions?

Try either C or Option.

Option was only bringing up a (for some strange reason) Windows partition. C brought up nothing else, but eventually loaded into Linux.

C should force it to boot from the install disk if it is loaded in the drive. Option will let you select any bootable drive in the computer, including the install disk if it is loaded. Does other optical media work in the computer?