Hello,
Windows ask you for administrator password when you attempt to install a program or when you try to run as administrator and so on.
If Windows ask you for root password when saving a file is because you are saving in a place you should not, for example c: or another user hard disk.
You have your own hard disk and there you should save your files.
The message telling you that you had no space left is because you are trying to save on c: (to let you understand is where windows is installed) .
Please lets speak more about this in ticket system and if you still want a refund then i'll issue a refund.
Regards.