Reinstalling isn't one of my recommended steps. We want to try recreating the preference files, which isn't necessarily done during an uninstall and does not require and uninstall to perform. The Preference file stores all of your settings. If you merely delete or rename this file, Lightroom will return to all of its default settings. If this file gets damaged, it will tell Lightroom to behave in unexpected ways. The file is stored here: Preference and other file locations in Lightroom 5
When you turn on your computer, you are logged into a user account. User accounts exist at the OS level of the system and are used to store your personal files and preferences. You create new user accounts in Control Panel > Users.
The Camera Raw plug-in doesn't have any effect on Lightroom, unless you send a raw file from Lightroom to Photoshop and if the versions mismatch, you'll get a warning.