I suggest you uninstall the application using its own uninstaller or Add or Remove Programs feature:
If you use Windows XP or bellow you can go to Start > Control Panel > Add or Remove Programs. In the Currently installed programs box, click on the RegCure 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 RegCure application and click on Uninstall.
After that, reinstall the program using the serial key received when your purchased it. In order to obtain a link to the official download, you can visit Software Informer review page of the product. Press the green Download button, save the file to your computer and install it following the provided instructions.