How to find and remove duplicate files ?

A hard drive is like a family garage--junk expands to fill available space. An SSD behaves very much the same way, but with less space.

A good duplicate file finder will help you reduce your digital junk levels. It can search for files with the same name, the same size, and/or the exact same contents. It helps you examine each file and decide which one to keep. It can ignore small files, so you can concentrate on the more wasteful redundancy.

I'm going to recommend two such programs, both free for non-commercial use.

All things considered, I recommend Digital Volcano's Duplicate Cleaner Free. The attractive, three-tab interface allows the program to provide plenty of options without overwhelming you.

When preparing Duplicate Cleaner for scanning your drive, you can have it examine or ignore file content. You can tell it to consider files with the same name, with similar names, or to ignore names completely. It can also match files by the Created and Modified Dates. A special Audio Mode tab helps you find duplicates of the same song by title, artist, and other such data.

If your hard drive is so overloaded that you hesitate to install even a 5MB program like Duplicate Cleaner Free, go with this old but still workable version of Easy Duplicate Finder. It's portable. You can download it on one computer, put it onto a flash drive, insert the flash drive into your PC, and run it without putting anything on the hard drive. It's not as versatile and easy to use as Duplicate Cleaner Free--or for that matter, as the current version of Easy Duplicate Finder, which is a reasonable alternative to Duplicate Cleaner.
But this old, portable version is not difficult either, and it works. It also has, oddly enough, an icon that makes me think of a public restroom.

Either of these programs should help you free up significant drive space--although you will have to face some decisions that only a human can make.

Searching for duplicate photos has its own challenges and requires specialized software. See Find duplicate photos for more on this.