Decrypt Wave files from an Addcom recorder system

The main objective of this project is to decrypt wave (.wav) files from our old phone recording system. Background: We had an ADD-COM recorder link pro system that was decommissioned and disposed of. No body bothered to check the software and pull out the key that was used to encrypt the wav files that were archived to CD. Task: 1. You need to decrypt the attached sample file so that it is playable via windows media player or VLC media player. 2. You must write a small application that can run in a windows XP or windows 7 environment, take one or many encrypted wav files as the arguement and output the playable version(s). This can be as simple as a command prompt based executable. 3. Hand over all the code. More useful information. All our archives should be encrypted with the same key, so if you crack the sample file you should be able to crack the rest. The "key" to the best of my knowledge is a set 6 to 9 numbers (maybe even more). We do not know what type of encryption is used to encrypt the file or what codec is used for the wav file. That's all the information I have, you may need to do research on your own to accomplish the task. Good luck