If you have a small hard drive, what can happen is that you can start to run out of room?
When clients need more space on their hard drive, what I do is load a program to look for the extremely large files, which have dates in them that are very old. Generally, these are very old backup files say five (5) year old plus. Also what I look for is video files, generally once people have seen them they no longer require them.
This program is called Wiztree can help you get more space but be careful before using it.