First, the Cable Select should be the best strapping method, as that is what is used from the factory.  Some have changed to the older Master/Slave method, but being a computer tech I try to keep my customers systems "unmodified" from factory settings as that usually aviods problems or potential problems.

However, I've had problems with some (not all) PC's with two CD/DVD burners installed.  I don't know why, but some will not work with two burners installed in the system.  Try physically removing the CD burner and see if that does anything for your problem, not just disabling them which really doesn't "uninstall" them.  Actually, all you have to do is unplug the IDE Ribbon cable to "remove" the drive for testing.

If there are any BIOS updates available from Dell for your specific model, you should also update as later BIOS' have support for additonal system devices.  Whether it will help your specific issue ??