Most of our netbooks have very little “disk” space. And it goes somewhere in the process of work, and, unfortunately, depending on the tasks, often quite quickly. I found a program that will help you quickly, with a few clicks, find the heaviest folders. I got the installer files and temprorary_downloads in Opera.
This program is called TreeSizeFree, distributed free of charge.

The program quite conveniently sorts the folders on the disk as they decrease the space they occupy, displaying in graphical and text form how much the folder takes. With a little knowledge of the system, you can safely delete some of them.
Thus, it is quite possible to postpone the slow death of Windows from the lack of space for another six months or a year (as someone).
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You can download it on the
JAM Software website.
UPD: See the comments, people offer a lot of alternative programs.
sequoiaview - Displays a graphic map of folders and files.
WinDirStat - the program is similar, but there is a conventional color map for file types (in fact, a mixture of TreeSize and SequoiaView).
Scanner - Displays information in the form of a pie chart, showing several levels in depth.