Have you ever used an online player? For example, online movie-watching software such as Fast Broadcast and PPLIVE, if any, may be that these players set the default cache area on the system disk, so every time you watch a movie, it will quietly put the video file on your system disk, so that your system disk space will become smaller unconsciously. Because I don't know what player you are using, I can't tell you exactly how to set it up. You can Baidu it. Then simply set the buffer path to another drive letter. Then move the buffered files under the system drive letter to the set buffer path (if you don't want to keep these videos, you can delete them directly. In addition, your software and games should not be installed on the system disk, which will occupy the system disk space on the one hand and affect the system speed on the other. In addition, pay attention to the download directory of the software you downloaded, and try to set it on other drive letters. I hope my answer can help you.