There are several reasons why Windows Live OneCare might not be able to scan a file for viruses. The file might be in use by a program, it might be protected by a password, or you might not have permissions (A rule associated with an object (such as a file) to regulate which users can gain access to the object and in what manner. Permissions are granted or denied by the object's owner, and can also be determined by the user account group to which a user belongs.) to view the file.
If the file is password protected and you know the password, all you have to do is open the file using the password and the file will be scanned automatically by Antivirus monitoring. Or you can remove the password protection from the file and and then run the virus scan again.
If you don’t have permission to access the file, you must contact the owner of the file or an administrator (An account that allows a user to perform actions that require special rights on a computer. A user with a computer administrator account can create, delete, and change all user accounts on the computer.
) to have the file scanned.