You can use the encryption tool to encrypt .wmv,.wma,.asf files, the encrypted media files can only be played after obtaining the Playback license provided by your webserver. You can set the following playback rights for your consumers on your webserver. Playcount - This right specifies the number of times the consumer is allowed to play the encrypted files. ExpirationDate - This right specifies a date after which the playback license is no longer valid and the encrypted file can no longer be played. For example, you can set a playback license to expire on December 31, 2004. ExpirationOnStore - This right specifies the length of time (in hours) a playback license is valid after the first time the playback license is stored on the consumer's computer. For example, you can set a license to expire 72 hours after it is stored.