then go into the Program Files folder for CC and delete its contents
(keep the .ini file if you have customised settings)
download the latest build from here; <span><a href="https://www.piriform.com/ccleaner/builds" rel="external nofollow">https://www.piriform.com/ccleaner/builds</a></span> (or use FileHippo for previous versions)
reboot the PC then install CC from your downloaded file.
if you need to convert this Free version to the Pro, go to Options > About and enter your license key.</p>
if no luck, try the install with the PC in Safe Mode.