You will need to encrypt the files as well, in addition to
creating an account for them. And warn them not to attempt in
changing your own windows account pw as that would lock you
out of your own files as well. Once the files are
encrypted, they are tied to your windows account AND
password.
If all these are too troublesome or risky, as mentioned by posters
above me, just get an external HDD or thumbdrive if it's just a few
small files.
