In versions 18 and under you will need to uninstall from old system within the Windows Control Panel >> Programs & Features. The uninstall process will generate an uninstall code. Please notify PRO Landscape Support with this code and we will remove the old system from the license. On the replacement system, install the program from the installation DVD. You must register the new system within 60 days to avoid being locked out of the software. On versions 19 or higher, open the software on the old computer and go to HELP >> REGISTRATION INFORMATION and write down the registration number. Uninstall the system in the Windows Control Panel >> Programs and Features and notify PRO Landscape Support that you removed this system by supplying the registration number, If an uninstall is not possible you can supply Support with the make and model of the old computer or provide the Registration Number from your other registered computer(Not the new computer). We can use this information to eliminate the old system. On the replacement system, install using the DVD, USB drive or download link originally supplied with your purchase. The system must be registered within 15 days.