Dvd-rw drive full?

I HAVE DONE THE DEFRAG (C DRIVE), DISC CLEAN UP, REMOVED TEMP AND UNWANTED FILES,VIDEOS ETC ERA, I DO NOT KOW WHAT ELSE TO DO? I WAS TRYING TO BURN A CD OF MUSIC AND WHEN PUTTING IN A BLANK DISC (TRIED 10 AND DIFFERENT MAKES) IT COME UP DISC ALREADY FULL? PLEASE HELP? IS IT POSSIBLE TO DEFRAG THE D DRIVE? OR AM I BEING TOTALLY SILLY? HEHEH THANKS ALOT, ANDY