If you use Windows XP or below navigate to Start > Control Panel > Add or Remove Programs. In the Currently installed programs box, click on the Dalet program and then click Remove.
If you have Windows Vista or above you need to go to Start > Control Panel > Programs > Programs and Features. Select the Dalet application and click on Uninstall.
After that, run a registry cleaner from Software Informer database to make sure that there are no leftover registry keys in your system and install the software again. This should fix it.