Spiros,
It sounds like you've taken the necessary steps, but to clarify:
The BeoMedia is intended for HD displays and comes set to HIGH 1. You have to connect a VGA monitor (which it sounds like you have to test the output) and change the video settings to STANDARD. Make sure you save the setting.
At that point you can connect it to a standard television and it should work.
There is scarcely anything in this world that some man cannot make a little worse and sell a little more cheaply. The person who buys on price alone is this man's lawful prey. - John Ruskin