That's because the number of temporary files in the system has increased, resulting in a decrease in disk C space. The size of C disk space will affect the running speed of the whole system. It is recommended that LZ clean the disk regularly. Or use professional software cclean. There are many softwares in this field, such as Optimizer, Super Rabbit, YourUninstaller and so on. Also, you can download a shadow system to protect drive C, so that the space of drive C will not shrink, and it can also effectively avoid viruses.