I came across this program called ‘Connectify’. It allows you to convert your Windows 7 PC into a portable internet sharing hotspot or local network. All you need is a WiFi adapter installed doesn’t matter if it’s B, G or N. You can play games on LAN, share files wirelessly without purchasing any external hardware. Moreover, you can encrypt your hotspot with WPA2 PSK for protection. Connectify has both paid and free version, free version is enough to create hotspots.
Edit: I found a freeware clone named mHotspot which does the same function as Connectify.