i just bought a 3tb external hardrive and its not working on my old media player which is also WD. plz help.
This seems fairly easy to answer. Since you have a new HD already, do NOT buy the WD media player (the HUB) with an internal HD; buy the WDTV Live Streaming Media Player (aka SMP). It is the only other current model available, and I am pretty sure it can take a 3TB drive. Others here can confirm or deny this statement.
