Cannot boot into mountain lion after I have set the start volume to CD drive
Previously I need to boot from CD so I have set the start volume to CD drive by pressing command+option+P+R at the same time and change the start up volume to CD drive.
But right now, it can just start from CD but cannot boot into Mac OS (Mountain Lion) which is installed in the hard disk.
I have tried to press command+option+P+R at teh same time during bootup but seems like right now it doesn't recognize this command. I have tried pressing "X" or "option" or spacebar, etc during bootup but still it tries to boot from CD.
Anyway I can change the start volume back to my internal hard disk?
I have even disassembled my iMac and the CD drive to remove the previous CD as well. Then it still tries to boot from CD drive but now saying the device is not bootable and ask me to insert a bootup disk. I then tried to put the Mountain lion installation DVD (I previously created the installation DVD by following the DIY way from this link http://www.cultofmac.com/180925/how-to-make-a-bootable-disk-or-usb-drive-of-os-x -mountain-lion/) there in the drive but it still said the device is not bootable.
I have disassembled my iMac again to remove the mountain lion disk right now. So the CD drive is now empty. Anyway I can change the start volume back to my internal hard disk?
This is really frustrating .. Hope someone can help.
thanks!