This is because the CAD system files appear damaged, the installation files to "repair or reinstall" can be, the specific steps are as follows:
1, click on the computer desktop "Start" icon, as follows Figure shows;
2, click the "Control Panel", as shown in the figure below;
3, click "Programs and Features", as shown in the figure below;
4, find "CAD ", right-click and then click "Uninstall/Change", as shown below;
5, click "Repair or reinstall" can be, as shown below.