Switching CDs in wiped macbook pro

spider island

Hello I have a strange problem. I have an old macbook I am trying to restore to 10.4.6. I accidentally put in a newer mac os CD I had laying around and used it to erase the hard drive. But because it is newer than what came on the computer I get a message that says "cannot be installed on this computer." I want to switch the cd for an older version of mac os X, but because the hard drive is wiped, I can only start from the cd that is in there. Opening disk utility and going to eject wont work because that disk is in use running disk utility. Restarting while holding down the eject button does not work either. It seems like I may have to pry the cd out and switch in mac os 10.4.6 while the computer is off, but it seems like there should be a more civilized way.
Eject the DVD by:
Restarting while holding the trackpad button down.
Keep holding the trackpad button.
Shortly after the screen lights up, the disk should slide right out.
Then, you can insert the disk that you really want.

Another method is to hold the Option key as you restart. You should see the boot manager screen appear, which will probably show one icon, for the DVD that's in the drive now. The DVD should eject by holding the eject key on the keyboard (should the the triangle in the top right corner. That should eject the DVD then, and you can put in the disk you want to use.
I read on another thread that you have a keyboard problem with the Y key.

Check in your System Preferences, then International pref pane. Click on the Input Menu tab. Check Keyboard Viewer in the list, then check the box "Show Input Menu in Menu Bar"
You'll see a flag menu in your menubar now. Click on that flag, and choose Keyboard Viewer. You can now test your keyboard, looking for keys that do not work, and keys that respond when not called. You may see that multiple keys respond when only one is pressed. You might also see that some keys stay selected, even after you release, or might respond to heavy "taps" before a particular key will release, or don't respond at all.
Let us know what you find out. Even an external keyboard may not help, if one or two keys on your internal keyboard are intermittent.