2nd level domain on unix with top on windows?

I want to set up a second-level domain (demo.mydomain.com) on a unix box but my main site is on a windows box (ie. www.mydomain.com is hosted here under a windows account). Is this possible? I don’t see a way in the CP to do it if so.

Thanks,
Tim

stopgap(win) + alias(win) + custom dns(linux)