DVD XCOPY only burns part of the movie (toshiba sd-r6012 drive)

I have a Toshiba DVD-Ram SD-R6012 drive and no matter what DVD copying program I use I get the same result. I've used DVD cloner, DVD shrink, Nero DVD 5, Xcopy xpress, xcopy gold, xcopy platnum, just to name a few. Xcopy reads the DVD fine and asks me to insert a blank. I do this and it starts burning for about 10-15 minutes. The drive opens and Xcopy says "Burn successful", but it only has about 15-20 minutes of the movie on the disk. I am running XP home and I have gone in to msconfig and deselected everything under the start menu/restarted my computer and tried to copy a DVD. (I get the same thing). I have been getting the same results for over a year and tried everything I can find on forums with no luck, but I keep trying. Please help!!!