Although I have had Ccleaner for some years, I have just tried for the first time, the Duplicate Finder.   Assuming the list shown were duplicates, I started marking with a tick, all of those shown.  However it went on and on, to the extent I have got cold feet as to what I might be doing.  Most of the files shown seemed to be for 2009.  Advice please.  Do I proceed and delete them all or not?    Many thanks.