What happens when you move the that system closer to the router?...that is if that's possible
If this is a desktop and you're using a wireless PCI style card see if you can move the antenna or replace it with one with a cable so you can move it around. If it's a usb stick with a build in antenna the only way to move it's antenna around is to get a USB extension cord and plug it into that then you can move it around.
Other laptops get more bars could be because they have better antennas
You could try changing the channel the router uses to one with less clutter (other routers around you using the same channel). To help figure out which channel will be best for you try inSSIDer http://www.metageek.net/products/inssider/..._expid=190328-1