I was recommended to use your product by another forum (Zone Alarm). I am interested in the registry portion for two reasons;
1) the possibility that a previous version of ZA has left things in the system.
2) after having Apple Quick time,I Tunes,Bonjour, and possibly more and then removed that portions of the above may still be left. In particular Bonjour Service sometimes I believe my computer is looking for this at start-up.
I am apprehensive about messing with the registry(and have read some FAQ's and posts).
The question would be if I am careful and use Ccleaners back-up tool should I be fairly safe?
Would the registry tool address the first two issues?
What about programs or documents that are seldom used(by me)?
Once I analyze the registry is it difficult to choose which items to omit?
When you clean you will be given the option to backup the items being removed (they will be saved in .reg format and you can right click and choose merge if you need to restore them)
Best practice is to follow the advice laid out in my signature.
Do it in small bits
Don't delete everything that is presented to you (in your case that shouldn't be an issue because you are seeking out certain applications)
Should ERUNT be used along with the registry cleaner or is Ccleanr's backup sufficient?
You can use ERUNT beforehand. Although you're better off to install the ERUNT package (pay attention to the instructions for your version of Windows if there are any) and let it automatically make daily backups for you. At some point you'll probably need to use an ERUNT backup -- but not necessarily from registry cleaning with CCleaner.