Do you have some CD-RW or DVD-RW discs that you need to erase, but weren't sure how to do it? This tip will require a writable CD drive or SuperDrive in your Mac, and some CD-RW or DVD-RW media.
Here is how to do it:
Click on the 'Finder' on your Dock.
Next, from the menu, choose 'Go -> Utilities'.
Now, launch the 'Disk Utility' app.
Now, insert your RW media into your optical CD or DVD drive. You will see your disc appear in the left pane of the Disk Utility window. Click on it to select it. Be sure you are NOT selecting you Macintosh Hard Drive. As a check, look the bottom of the Disk Utility window and it will show a description of whatever disc you have selected. It should have CD and DVDs listed under the capabilities. Next, select the 'Erase' tab and then either enable or disable 'Quick Erase'. If you choose to leave Quick Erase enabled, it will simply wipe the Table of Contents, but doesn't erase the data at this time. I typically use this -- but if you need more security and don't want any previous data recovered, it's a good idea to disable 'Quick Erase'. With it disabled, Disk Utility will write Zeroes to every spot on the disc. When you are ready, click 'Erase'. Disk Utility will warn you about erasing the data. If you are sure, click 'Erase' again
When it is done, you will have a blank disc waiting for you.