Vista - User Account Issues?

I'm speaking to a customer about User account issues on Vista Home Basic.
Aparently, when she added an account for her daughter. That came out fine,
but when she logged back into her account all of her information was missing.
After speaking to us for a few moments, we rebooted her computer because of
a remote access issue. When she rebooted the files where, somehow, returned
to her computer. There is not a single support document I could find about
how or why this may happen, or even how to prevent this if it where to happen
again. Would anyone else have any information as to how or why this happens?