Why can't I delete a file off a rewritable CD (CD-RW)?

A CD-RW (Compact Disc-ReWritable), introduced in 1997, is a rewritable optical disc. CD-RWs can be written to hundreds of times as compared to a CD-R (Compact Disc-Recordable), which can only be written to once.

Let’s say you have burned your files onto a rewritable CD.  When you try to delete a file off the CD, you get a message that you are not able to do so because the files are read-only.  Shouldn’t you be able to write files on the CD then add or delete files as you please since it is rewritable?

In general, rewritable CDs must first be erased totally, not just in parts, before they can be reused. Once a file is written on a rewritable disc, it remains to be read-only. That means it cannot be overwritten or saved over one file at a time.

However, the Live File System, which uses Universal Disk Format (UDF) was introduced in Windows Vista.  The Live File System allows files to be saved, deleted and edited on the CD-RW itself just as it would on removable media like floppy disks and USB flash drives. This is also possible on write-once media, such as CD-R, but in that case the space occupied by the deleted files cannot be reclaimed and instead becomes inaccessible.

On a computer running Windows Vista or later, your CD-RW must first be formatted using UDF.  To do this, insert your blank CD-RW in the computer and in the Computer window, double-click on the drive that contains your blank disc.  The “Burn a Disc” dialogue box comes up with two choices of how you want the disc to be used. The first choice is to use the disc like a USB flash drive using the Live File System.  This will format your disc using UDF, which will then allow you to delete a single file at a time on a Windows machine. The other choice is to use the disc  to burn files that cannot be edited or removed. This uses the Mastered format, which is often used when you need a disc that will play on any computer or in some different consumer electronic devices, such as CD, DVD, and Blu-ray Disc players, that can play digital music files, pictures, or video files.

On a Mac, deleting a file off a CD-RW can only be done in Mac OS X 10.5 or later, where the newfs_udf command utility must be used.  More information on how to use the newfs_udf utility may be found in the Mac OS X Developer Library in Apple’s website.


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