Please clarify. Did you try to make a straight copy of a commercial disc? If so, you must decrypt the disc first. Then, if trying to fit it on a single layer recordable, you generally must transcode or re-encode. Look here:
http://www.mrbass.org/
Get DVDShrink and DVDDecrypter, and be sure to read a couple guides. If neither works, you probably have an ARccOS disc (Sony, et.al.). That's a bit more complicated, but doable. Post back and good luck.
