If you don't then it's got to be user profile corruption, in which case I'd just delete the account from the other one and elect to save the user data from the account being deleted on your desktop.
Were I you I would create a new account, whether as a local account or another one that links to the same or a different Microsoft Account, and see if you have the same issues. If that's not what you're trying to do (and it sounds like it isn't - and you should expect to have to grant elevated permissions on those occasions when you are) and are still experiencing this problem this suggests a probable corruption of the user profile for the account you're using with admin privilege. There are very good reasons that Windows itself tries to prevent anyone, including someone with admin privilege, from writing to the OS's root folder on whim. While I agree that everyone has the right to manage their data their own way, what several of us were trying to discern is whether you were routinely trying to save user data files in the root directory, that is, C:\
