Cimatron 13 can be installed without removing the previous Cimatron E12 version. While each version requires its own specific license file, they can be kept in the same folder. Cimatron E12 and 13 can even be used simultaneously. Saving a file, however, is not backward compatible. Once saved in version 13, you will not be able to open the file in version 12.
When opening a Cimatron file directly from Windows, the system will start the last ‘active’ version of Cimatron, which may be version 12. To make 13 the active version, use the utility on the Cimatron 13 control panel.