Media Centre is a program that runs on Win XP/Vista it is not the OS lol.
So if you can see the picture ok then it will work. If your after wierd resolutions then normally it is down to the monitor driver file and what your gfx card driver supports.
I bought a logitech keyboard/mouse/remote which came with a media centre prog which is very good 🙂 Only cost £35 and have that running on my media pc with Windows XP Lite.
I also have a Mitsubishi MegaView 30″ tv/monitor that support 70hz up to 1024×768 and will do the proper DVD resolutions in between. but its all determined by the monitor driver i have for it.