Here I will explain how to use an application called "Duplicate Cleaner" to free up space on your windows pc.
The program offers different ways to search for the files and different actions to apply.

In this example I will take in consideration how to search for duplicate files (on the same partition) depending on their content and making "Hard Links" of these files.
Please make sure your Partition is NTFS, this method doesn't work for FAT32.
If your partition is FAT32 you can convert it easily to NTFS using this command from the command line: CONVERT D: /FS:NTFS
(Example for partition D:)


You can click on Hard Link to learn more about it, in few words a Hard Link keeps duplicate files in different paths but occupy only the space of one file on your hard disk.

Here are the steps:

1.  Download and install Duplicate Cleaner from: http://www.digitalvolcano.co.uk/dupe.html

2. open Duplicate Cleaner and from the search criteria choose only one partition of your choice, in this tutorial I will choose partition D: and add it to the search path.
From File Search Choose the Filter to be *.*;* and check same Content(CRC). Minimum File Size: 100 KB
Also when you click on Options at the upper toolbar check all options you see.

 Duplicate Cleaner options


Duplicate Cleaner Options

3. Click Go

4. When the scan is complete click on Selection Assistant

5. At the lower left corner where it says Select for deletion by group, choose:
select all but one file in each group
then click select and close.

6. Now click on Remove selected and make click on Create Hardlinks.

Then you are done!
By this you free up space without deleting files.

I'm glad to receive your questions, please comment below.