I have tried using CCleaner but it doesn't find truly duplicate files... What I want is something that will tell me which files are true duplicates. If my question is unclear or needs elaboration please let me know.
Consider using one that does this:
-scans the computer and lists duplicate files based on Byte for Byte Comparison or Advanced Scan (CRC, SHA-1 hash). It can find duplicates of any files: documents, music, video, images etc. (MD5 is said to be 'near enough for practical use'- whatever that means).
- and has appropriate filters and options to limit the search (by path, file type, size....), and offer a review before deletion (think pictures, music).
However, most good ones are not free.
Another problem is that many don't state whether they use the matching criteria on their web site.
It's hard to make a general recommendation as some tools specialise in matching media files, for example.
There are plenty of comparison lists.
AllDup looks interesting:
7 Free And Efficient Duplicate Files Finder For Windows And macOS | GeckoandFly 2018
Note that Ccleaner's comparison has byte-for-byte comparison off by default, which is perhaps why it doesn't seem so accurate.
More here:
10 Best Free Duplicate File Finder and Remover Software for Windows 2018
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