Changing the Default Drawing Editor Program

Does anyone know how to change my drawing editor to defualtfrom SolidWorks' Drawing Editor to AutoCAD? I have AutoCAD LT on myPC and for some reason when I installed the latest service pack,all of my .dwg files have been defualted to open with theSolidWorks Drawing Editor Program.

Any help would be greatly appreciated.SolidworksDrawings And Detailing