Poweriso and dvd-ram

I have a toshiba laptop that has an ‘HL-DT-ST-DVDRAM GSA-T40N’ drive.
I use PowerISO 4.3 to handle my media, but I need your help. I can’t find a way to delete individual files from dvd-rw media. I’m able only to replace the whole content with new ones. I see a ‘Delete’ button on the tool bar, but its always dimmed.

How can I delete individual files from dvd-rw disks using PowerISO?
Or do I need another program to use? I don’t like nero because its too slow and bulky with unneeded tools.
I’m using Windows 7


you can’t delete individual files from a -/+RW disc. So you need the entire content to your HDD and reburn the disc leaving out the files you don’t want to have on the disc.