Really long s-video cable?
Here's a long cheap one but I'm not sure how the quality would be for a run that long. I'd say get an s-video cable as short as you can to do the run.
I don't know if there's a good wireless method, and if there is, it's probably pricey.
If you can, just move the computer to the other room and you'll get the best quality picture from the shorter run etc.
I'm not really sure how long a run a videocard will be able to run a signal well.