Erase Write Protected Cd-RWI have a Memorex Cd

I have a Memorex Cd-rw that is write protected. I have gone as far a right clicking on the file on the disc, clicked on Properties, and tried to uncheck the Read-Only box in Attributes , but an Access Denied Warning comes up that says I need to "provide administrator permission to change these attributes". I click the Continue button and another Warning comes up that says "an error occured applying attributes to the file. access denied. I run the computer as the administrator.
I know that I could just throw this Cd-rw away, but I would love to be able to learn how to beat this thing. Thanks in advance for helping me.

 

Try CDBurnerXP. It has an erase function that may have better luck. (Pay attention during install to make sure you opt out of any unnecessary toolbars as they may be bundled advertising. The program itself is a very good burning software and should erase your disc.)