So I rebooted my computer after a crash, and after logging in the screens were completely black and my mouse & keyboard was unresponsive. I did Crtl + Alt + Del which brought up the correct menu, and after I exited it I was put onto the start menu, which was blank. Just like the login screen and lock screen, the colour and design had been reset (to purple, if it matters). Leaving the start menu presents me with the black desktop again, but the start bar at the bottom is present and after a while the clock, wifi, volume etc. loads in the bottom right as well as a User Profile Service notification telling me I've been "signed in with the default profile for the system". There are no pinned apps either, although FileZilla Server loads up after a minute and that is on the start bar now. Also, immediately after leaving the start menu, a "Location is not available" dialogue box comes up with the error message:
When I click OK on that, the Recycle Bin appears on my desktop. Opening the recycle bin displays the same message as before, and it does have all of the recycled files and folders inside. From here I can navigate through my folders, although the libraries option on the left side is empty (it normally has my documents, videos, user folder etc.). If I navigate to D:\Users\Administrator, my desktop folder is there with everything inside. I can also type Google (or presumably anything after http://) into the explorer bar which opens up Google Chrome, as well as open cmd and Control Panel by typing each one in. Navigating to C:\Windows\system32\config\systemprofile shows that \Desktop isn't actually present any more.C:\Windows\system32\config\systemprofile\Desktop refers to a location that is unavailable. It could be on a hard drive on this computer or on a network. Check to make sure that the disk is properly inserted, or that you are connected to the Internet or your network, then try again. If it still cannot be located, the information might have been moved to a different location.
I've tried using both elevated cmd (net user /add Username) and control panel to create a new user, but the control panel button "Add or remove user accounts" button is unresponsive, and although cmd gives me a successful operation message (and tells me the account already exists if I do the same command again), it doesn't show up on the logon screen. I've tried making the user through cmd while logged in to administrator, using the Advanced Startup Options command prompt (the one that uses X:\) and using safe mode with command prompt. The right-corner-menu > Settings > Change PC Settings button is unresponsive. I can't use the built-in administrator account because after I similar occurrence before, I've been using the built-in admin, which is the one that is now broken. None of my older accounts show up, either.
Also, after a few restarts and many attempted fixes (mainly automatic repair etc.), it now plays the whole patronising "We're getting your PC ready" video whenever I try to log in, and then it displays the start menu and bar (so I don't need to do the Crtl + Alt + Del step).
Sorry if this is a big wall of text, any help is appreciated.