Opening a .Bin file on mac?

Hi,

I have got a .bin file on my mac that is 255mb big, and should contain a load of music samples in it, but when i double click it, it says' archiving, like its unzipping it or something, but nothing happens, it just creates a slightly smaller file with the extension .bin.cpgz

Anyone know how i can get at the contents of this .bin file please?

Thank you for any help and suggestions.

Tom