iTunes: Cannot Install From Software Install Disc

You cannot install iTunes from the Software Install disc if it is also the startup disk.
Symptom

When you try to install iTunes from the Software Install disc, an alert box appears with a message that says the disk is locked and the installation cannot take place.

Solution

The iTunes installer cannot install software on your computer's hard disk if the Software Install disc was used to start up the computer. Restart the computer using the hard disk as the startup disk, or follow these steps:
Published Date: Feb 18, 2012