I have just compiled the steps that worked for me here all in one page (with screen shots).
That file needs to be saved in your C:\Program Files\Sling Media\SlingPlayer\SBAV folder.
Goto Setup Assistant on your Slingbox. And Select Configure Video Sources.
Select your Connection and Choose Cable Box.
Select Comcast as the manufacture and Other for the model.
Make sure the Lineup is correct, and hit next. And now you will have to select your code to be able to control your DC50X DTA. In the Select Code box, select Custom and type in C2000. Then hit the Power button to test. Remember that the DC50X does not turn off, this will not turn off the box. But it will upload the RNG200 bin file. If you get an error message, make sure you have saved the RNG200 bin file in the correct place.
Now just finish up the Setup Assistant, and you will be good.