Hello,
Maybe you'd better provide more information on what you mean by ARPCache..
So I guess you mean the Add Remove Programs Cache ?... what is actually under the following registry key :
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Management\ARPCache
(not to be confused with the Address Resolution Protocol Cache I guess )
I have read somewhere that this registrey key contains extra information, such as , size , frequency of use, last used on, that can be seen in the Add/Remove Programs list of Applications installed.
So I suppose it is not a real good idea to only zap everything in it, but to fine tune what stuff can be actually removed , at least related to Applications that have been already uninstalled. That is what is probably tricky to analyse...
Hope my answer satisfies you .. but probably best to be corrected or confirmed by the CCleaner developer