Personally I am quite happy with CCleaner as it is and with it's stock settings. I don't know anything about this CCleaner Enhancer and whilst I wouldn't suggest anything underhand, I don't see it mentioned at CCleaner's home web site at http://www.piriform.com/
So, may I ask why you want to add this to CCleaner? Adding 3rd party add-ons to software is always a bit of a worry for me, especially when I see no mention of them in the developers own web site.
What is the exact wording of the error message? it may be that the PATH is incorrect.
Mark
I just downloaded, and tried to install the ccleaner enhancer, but during the installation process it said that ccleaner was not installed. Ccleaner is installed. Any Ideas why this is happening. I already uninstalled, and reinstalled.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic