Just a thought. I presume you've been swapping the connection between your old PC and the new one when testing things for me. Have you been rebooting the STB each time? You need to else it won't talk properly to the Vista PC.
Can you also run the ipconfig command on the old PC so I can find out what IP address it's using?
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Do you know that we're all in line for succession to the throne? Really?
Well, if forty-eight million, two hundred thousand, seven hundred and one people died I'd be Queen.