If you cannot boot into VRChat or VRChat gets stuck on loading there are a few things you can try:

  1. You can re-run the installer to re-install VRChat
  2. In your  '%Userprofile%/AppData/LocalLow/VRChat/vrchat' folder there is a file called parse.settings. Try to rename this to parse.settings.bak and relaunch VRChat.
  3. If you still cannot get into VRChat try to rename the entire '%Userprofile%/AppData/LocalLow/VRChat' folder to 'VRChat_bak' and reinstall VRChat. Then try to load VRChat.