Windows 7 has an awesome utility called netsh that allows you to create wifi networks, even if you’re already connected to a wifi network on the same interface, which is actually slightly better than the same feature on OS X. If you don’t want to play with the command-line, there’s a handy utility called Connectify that makes creating a wifi hotspot from your Windows 7 box a breeze. This was one of the things I missed most about my Mac laptops.