what router are you using? There is a lot of do it yourself ghetto mod out there that you can do to help you boost the signal. Here are some of them that i came across. Most are done on the router end. But there are couple can be done on the wireless network card end as well. But will require more work =)
http://www.freeantennas.com/projects...te2/index.html
This site provide you the template for this project. Just save print it on a paper then trace it on to a folder paper. Then tape some tin foil paper on it. Although i haven't tried any of these myself. Since i had no problem with my wifi. But i do keep them in mind for future references in case i need a cheap way to fix a signal.