This is probably more likely a problem with my operating system, Windows XP, SP2, than CCleaner.  I just installed the latest version 5.4 over an older version, 3.01, which was working fine. But when I try to start the new version I get the following error message: "The procedure entry point GetLogicalProcessorInformation could not be located in the dynamic link library KERNEL32.dll".  I suspect this is because it was expecting the SP3 KERNEL32.dll? Since I am about to retire this PC in the near future, I don't want to install service pack 3 to find out if it will solve the problem (I am not even sure if pack 3 is still available).  So, I would appreciate any suggestions on how I might get version 5.4 to work on SP2.  I have yet to uninstall and reinstall v5.4 to see if it was a bad installation. As a side note, the reason I wanted to upgrade CCleaner was because I read where the newer versions are capable of cleaning out Firefox cache2 entries which are now filling up my hard drive with gigabytes of content that I can't seem to get rid of by telling Firefox to clean out my cache.