Older Powerbooks and Power PC's will not burn DVD+R Media.
To check your SYStem Profiler. Click on your Apple and then choose About this Mac and then choose More INFO, and then ATA and it will tell you the Optical Drive Installed in your machine.
Many times you will have to type in your Optical drive in a Google Search and find any and all Firmware updates for your particular Drive, some will have Firmware to help some do not.
Here is some GOOD INFO.
DVD-R Media is the most widely used and recognised media that can be used across the board on more computers and players then anything else out there.
That being said almost everyone of us have used the cheapest Media we could get and expect it to work.(WRONG) There is such a wide variety of poor quality media out there that just simply will not work, or if it does you might get lucky and get 1 or 2 to work even if it is minus R media that is the most widely recognised. Cheap Media is not the way to go.
Here are 2 links that will cover both aspects of Format and Quality.
I have found that the use of the best quality media has rendered the absolute best results.
FORMAT.
http://www.videohelp.com/dvd
QUALITY.
http://www.digitalfaq.com/media/dvdmedia.htm
I have found Maxell 16X DVD-R Media excellent.
Be sure you read th packaging, This media will burn on both the older computers that will only burn at 1X and 2X and the newer at the higher speeds.
Don