There is a flaw in windows that causes it to grab and advertise a wireless net called free public wifi. This is true even in a post service pack 2 machine! There is a special patch that Microsoft made just for this problem, but you have to get it yourself, it does not get delivered with normal updates. This problem was discussed in the Security Now net cast #82.
I bring this up now because in the library I work in, a patron had this problem. Their laptop had grabbed the free public wifi from some one else and was advertising it as a network. They could not attach to our hot spot because of this. As a quick fix I removed the free public wifi and attached to our hot spot. I then went into the advanced properties and turned off the automatically attach to preferred networks. The long term fix is to install the patch listed above.
By itself this is mostly a annoying. There is a chance thought that someone could use this flaw to connect to your laptop and access any shared folders or files you have. To help stop unwanted connecting be sure to turn off hyour net card when in a public area and are not using a wifi connection in the area.