After searching on the internet, it seems that there are some people who claim that the drive sets the book type as DVD-ROM by default. To test this claim, insert a previously burned DVD+R DL and go to ImgBurn Discovery mode. In the box on the right, you should see the name of your DVD drive at the top, followed by "Current Profile: DVD+R DL." This will be displayed even if the bitsetting occurs. Scroll down to Disc Information, and there should be an entry for Book Type. If it says DVD-ROM, then the bitsetting was successful and the problem is simply that your DVD player is physically incompatible with DVD+R DL and you need to get a new player if you want to be able to play such discs. If it says DVD+R DL, then the bitsetting was unsuccessful, and I can't really help you because I don't have the drive.