Because my TeXstudio cannot handle KaiTi fonts. Then I installed CTex trying to fix it. However, it gets my LaTeX totally broken. The reinstallation need the uninstalling of MikTex which cannot be finished.
Firstly, I used hardwipe which wiped everything but not some empty folder left. MikTex still cannot be installed.
Finally, I used unlocker to delete those empty folders. Though the folder is undeletable, unlocker set it get deleted at boot.
Voila! After a reboot, those folders disappear. And I get my MikTex and TeXstudio reinstalled.