Open Task Manager and EndTask any running CCleaner processes, then try the uninstall again. If that doesn't help perhaps uninstalling it by a different more robust means will work with either of the two freeware uninstallers linked below. Seriously, WTF is this? A more robust means????? No. You uninstall things by clicking uninstall. Only s***ty virus crapware you need to uninstall by more robust means.
Cure is worse than the disease. There is only one reason to install this software and it is to remove crap from your computer. But after you install it, ccleaner does not show up in the uninstall program list in windows control panel so you have to install other software to remove it, then uninstall that software This is crapware. The only reason to install cclearner is to clean crap running in the background but ccleaner is just another crapware program running in the background.