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 ZoomBrowser EX 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 ZoomBrowser EX application and click on Uninstall.
After that, go to Canon Support page, identify your camera model, select your operating system if it is not automatically detected and download and install the latest version of the application. This should fix the issue.