DVD/CD Trouble

Having bought ten discs from a local retailer for burning purposes have now discovered that they are non rewritable. What i mean by that is that i have burnt some photos to one, wanted to delete a photo from the disc, the computer says that i don't have enough privleges to do this. The discs i bought were Philips DVD+RW. The chap in the shop said they would be fine for what a wanted to do. (That is send data and delete data to and from them).

As posted earlier i have a iMAC G5 with a superdrive. I have being looking around the different types of media but cannot get my head round which one i need to be able to back up and delete photos/music/documents as necessary.

Could somebody point me in the right direction for the right type of media, or if i already have the right type of media, what am i doing wrong on my mac to be able to burn/delete data frm these discs.

Much appreciated for any info.
Thanks

Edit>> Just been looking on Mac Info on my comp and it says this about the media below OVERWRITEABLE YES. It must be something I am doing wrong to make the disc's non writeable on first burn. In the light of this can anyone help???

MAT****A DVD-R UJ-846:

Firmware Revision: FA0G
Interconnect: ATAPI
Burn Support: Yes (Apple Shipped/Supported)
Cache: 2048 KB
Reads DVD: Yes
CD-Write: -R, -RW
DVD-Write: -R, -RW, +R, +RW, +R DL
Burn Underrun Protection CD: Yes
Burn Underrun Protection DVD: Yes
Write Strategies: CD-TAO, CD-SAO, DVD-DAO
Media:
Media Type: DVD+RW
Blank: Yes
Erasable: Yes
Overwritable: Yes
Appendable: Yes

anyone??, 15 views and no one knows how to do this??

I am no expert on this Heysidays, however it has to do with how the program you are using closes the disc. DVD-RW/+RW can be closed and finalized to where no data on the disc can be erased or blank portions of the disc will no longer be available to be written to.

I would read the help me file in the application you are using looking specifically for using RW discs adn how to close them so the information is still available for deletion/addition of files.