MTS2000 Programing error

I'm trying to program a MTS2000 800 mhz for conventional an I get an error Cannot Write Radio without Advanced System Keys ! I have seen post where one guy can write to the radio on conventional without the Advanced System Keys without any problems . I'm using MTS2000 CPS VR02.03.00 and the Radio is is a MTS2000 R08.73. How do I disable the trunking so I will not have that System Key Error ??