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120gb zune player. battery has weakened over time and I want to replace it but I am not sure what generation it is.

g dosch, based on the 120GB storage space alone, this would be a 3rd gen. The following generation is the HD and it does not have that capacity, nor did any of the preceding generations. Besides the larger capacity, there was also a firmware update for the Zune, Anyhow, the battery is readily available at places like this. If you need any instructions, check on here. Hope this helps, good luck