Most of the boxes are locked in this regard

Some of the older Motorola boxes did permit some content to be exported via firewire port when used in combination with a freely downloadable software driver, but much of it was 5C protected. That means it can only be viewed while residing on the internal hard drive/with the DVR. Copyright stinks sometimes, but that's the current state of affairs.

There may be some grey market products available, but such discussion is not permitted here. You will have to look around elsewhere if such a solution still exists for your particular hardware/provider.