Shouldn't be a problem.
I'm guessing your TV tuner will differentiate between broadcast signals and a video input.
If you don't have software already (or even if you do), I recommend a little freeware program called Dscaler
. I dunno if it's completely compatible with your tuner, but it de-interlaces video to give a real purrty picture.
Dunno how long you can play with an Xbox AND a laptop crushing your nads though