File decryption

Recently a user left the company I work for on bad terms and encrypted some .wma files which we now need to convert to mp3 or .wav files to use for a presentation.

I do not know with which sw they have been encrypted but when I try to convert these files i get a message similar to ‘The file is encrypted and ‘the software’ is not able to decode.’
I know this is a shot in the dark but is there any generic type decryption sw that I can use to attempt to salvage these files. Thanks.