You won't be able to copy the entire contents of the dual-layer disc onto a single-layer disc because the two can't hold the same amount of data. Dual-layer discs hold 8.x GB and single-layers hold 4.x GB. If your burner is a dual-layer burner, then you can buy dual-layer discs and make copies just fine.
You might be able to achieve a copy if you compress the audio or video, but I wouldn't want to do that personally. Instead, I would delete content that wasn't necessary. For example, subtitles and extra features on a DVD movie could be cut from the copy so that the entire movie fits on a single-layer DVD.
Ep, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS