Make sure the hardware lock is firmly attached to the back of the machine. Once this has been confirmed, browse to your FlexCAD 3.63D install CD. From the CD, run D:\License\Rainbow\WIN_NT\SetupX86.exe. Once the window comes up, select Functions >> Install Sentinel Driver from the pull-down menu. A window will pop up with a path prompt; click OK. You will then be prompted that the instsallation was successful and to restart the machine.