This is the software publishers description:

DoubleKiller searches single or multiple directories for duplicate files by comparing any combination of file name, size, modification date and content. Using user-defined masks like *.mp3 or *.dll you can limit the scan to files that interest you or protect important files from being scanned. Furthermore you can exclude files in a particular file size range or files with certain attributes, like hidden or system files.

When the scan is finished a list containing all duplicates found is displayed and you can manually or automatically select the files to be removed. The result list can be sorted and exported to a textfile readable by both humans and spreadsheet applications.

DoubleKiller is a stand-alone executable that does not need to be installed, just extracted and run, and does not alter the system in any way without the user's prior permission