A CD that is write protected does not permit additions or other changes to its content. Perhaps it once made sense to for your disc's content to be thus safeguarded, but you now wish to revise or erase its contents. To do so, you will have to disable the CD write protection. With floppy disks, you could usually do this by moving a lever at the bottom edge of the disk. With CDs, you must change a software setting.
Click on the Windows "Start" menu and click on "My Computer" to access your computer directory.
Click into the top level of the "My Computer" directory tree. You should see listings for the C: drive and for the drive assigned to the CD, perhaps the D: drive or E: drive.
Right-click on the D: drive (or whichever drive is assigned to the CD). Select "Properties."
Click on the "Recording" tab (the fifth tab along the top of the "Properties" pop-up box).
Check the box for "Enable CD recording on this drive."
Choose a drive from the scroll box immediately below this setting to which Windows can store an image of the CD. Typically this will be the C: drive.
Check whether the CD is now writable by transferring a small file from your computer to the CD as a test. Then delete or remove the test file.