DVR Hard Drive reset of the 6412 

1. DCT6412 should be turned on
2. Press Cable, Power off, ok/Select, to bring up the Diagnostics Page
3. With diagnostics page showing press Replay (15-sec rewind), DVR, DVR, DVR, Live. 
4. 6412 now should show "Clr" in the LED display.
5. Press ok/Select to proceed with the reset (and presumably Exit to cancel).
6. The 6412 should now reset and download the Guide data from the Local headend