Previously, I had always believed that the only way you could create a fake (aka virtual) access point was using a wireless card that supported monitor mode, Linux, and software like hostapd. Well, with the introduction of Windows Vista/7, Microsoft now requires certified drivers to support monitor mode, which allows the user to (among other things) create virtual access points.
Two free programs that take advantage of this are Connectify (free) and an open-source project (currently in beta) called Virtual Router. Turning your internet connected system into an access point can be useful for certain types of penetration testing, as well...