I backed up some pics from a catalog in Photoshop element last night. Did some additional work on it today. I tried to back up the pics that I added on the same RW disc. Program said that data EXISTED on the disc & that I would have to erase that info before I could back up again. It looks like the RW discs cannot have info added to them. You must erase the old data before re-writing. Is this correct? TIA for the help.If you want to add data to RW disks you can do it two ways

1. Burn the disk as "multisession". When you need to add data later, choose the option in your BURNING software to import previous SESSION. Then add the data and burn another session. You can do this until the disk is full.

2. Install "packet writing" software. One well known product is Nero InCD. This allows you to format the disk like a hard drive or giant floppy disk. You can add, REPLACE and delete files. You can do this by drag-and-drop in Windows Explorer. Some drawbacks are that it can be slow and your data is not 100% safe, but that applies to RW disks in general. Many people do not like packet writing.