I like CCleaner. At least twice it has helped me take care of problems. Recently, after uninstalling/reinstalling Portable Libre Office, I ended up not being able to set Calc to open Excel files. After a while, after uninstalling and reinstalling a few times, when I ran CCleaners registry cleaner, I saw an entry that clearly was the fix to my troubles. After deleting the entry, I was once again able to set Calc as the default program to open Excel files. Bo