Ummm at least get a usb adapter that has a movable antenna on it, or one that is still usb with a long wire and a tabetop setup to help with the signal.
Even better would be a wireless N router... like this one. But you would have to buy a wireless n usb card to benefit the most from the router.
http://www.amazon.com/Cisco-Linksys-WRT160NL-Wireless-N-Broadband-Compatible/dp/B0028N6VLE