If you use Windows XP or below you can go to Start > Control Panel > Add or Remove Programs. In the Currently installed programs box, click on the Tango PCB program and then click Repair. If it doesn't have the Repair option, click Remove, uninstall the software and then install it again.
If you have Windows Vista or above you need to go to Start > Control Panel > Programs > Programs and Features. Select the Tango PCB application and click on Repair. Also, if it doesn't have the Repair option, click Uninstall, remove the software and then install it again.