Don't just look at this folder, look at Windows or drive C, which is the cache file of the system and the application. Pay attention to install the software in D or other files, and other softwares that often use browsers, watch movies, set general files and cache user data will be stored in drive C by default. After a long time, you can use system security software to clean up garbage, cache and registry, such as 360 or Jinshan, depending on which one you like. My system is 3 years old, Win7, partition 50G, and now it is 25G.