What does the HDHomeRun Setup do?
In case you need to manually tweak the HDHR Setup, here is what the automated setup does does.
First, it creates the ATSC mapping for Vista Media Center. That is, it tells VMC what “4.1″ translates to, along with the call sign. This is written to the atscprefs.xml file, located in the C:\ProgramData\Microsoft\eHome\EPG\Prefs directory. You can modify it by right-clicking and selecting Edit.
As you can see, it looks similar to the data you see in the HDHR Setup screens. VMC uses this data to determine which channels are which.
Second, it creates a mapping file used by HDHR’s BDA driver, which acts as a wrapper to allow Vista to “see” QAM channels. This file is called “Digital Cable.xml” and is located in the C:\ProgramData\SiliconDust\HDHomeRun\ directory. You can modify it by right-clicking and selecting Edit.
This is what the setup process obscures for you. Each QAM channel has modulation and frequency information associated with it. The setup process captures all of this for you.
Don’t forget that any changes to the atscprefs.xml file requires you run the guided setup in VMC again. Changes to “Digital Cable.xml” do not require the VMC guided setup (because the changes are transparent to VMC).