Hello and welcome to THE forum Windows XP Media Center is basically XP Professional without domain support and media center components added. Have you tried your device in a machine running XP Pro and it was OK?
First off, hello and welcome to THE forum Second, just use Vista a bit longer then image it and install XP if you really don't like Vista. Remember that you can downgrade the Vista licence to XP by calling Microsoft hotline.
If your Windows desktop resolution is set to say 1280 x 1024 @ 75Hz and the monitor in question does not support that resolution, it will stay black. On a different note, do you see the POST at all?
How do you connect to the internet? Cable, modem, wireless? If the drivers for your device used to connect to the internet are loaded in Safe Mode, then yes, you can connect.
From reading your error message it appears that the multiplayer executable is at fault. Have you tried to reinstall the game? Ona side note, are you using any cracks?
Those types of (human) errors are quite common... I remember when I networked some ~15 pc's for a small company and the evening before I was invited to a party with lots of beer. Needless to say that I shoved the SAME IP address in every pc then wondered where the heck those IP conflict pop-ups come from