Well . . . Yes, it is designed to reformat any EHD that has not yet been formatted for your Dish account and encryption system. So, no, the Dish EHD can ONLY be used for Dish transfers and not other purposes. One can not have multiple uses for a Dish EHD.
However, if you decide you no longer want to use the EHD as a Dish EHD for transfers, you can use your PC to reformat the EHD and then use it as you would any other EHD for Windows or whatever OS.
The content providers and owners have required Dish to design the transfer feature in such as way as to prevent any other way to access the recordings, decrypt the recordings, or transfer them to any other place than the Hopper/s on the account from which they came (or replacement Hopper tied to your account), and all transfers are tied to the original ONE account. So, NO. No one of typical consumer ability is capable of circumventing these restrictions, otherwise, the content providers/owners would NEVER allow such a great archiving/transfer feature.
There is no hack talk here, so you are on your own from this point, but such circumvention is a violation of the terms of agreement.