Apparently MS have included a lot of unused code in W7 that allows a PC to use it's WiFi adaptor as a standard connection to the Internet and concurrently as a Virtual Adaptor acting as an Access Point. So you can connect by WiFi using your User name and Password but at the same time allow others to access the system using your own Access Point SSID and Encryption Password. To activate this ability you need a free program from click here It's not 100% on all adaptors but does work on a lot. I tried and my adaptor isn't supported and Connectify quickly replied to my email with:

Connectify works with new Windows 7 logo-tested WiFi devices, and many older devices that have compatible Windows 7 drivers. There are a number of Intel WiFi devices that do not have proper driver support. We are working on a solution that will allow Connectify to work with all WiFi devices (and even older versions of Windows) and will make an announcement when we have a resolution.

These older devices are known to be compatible:

Ralink RT2870 (in many 802.11n USB dongles)
Broadcom 4310-series (in many Dell laptops)
Realtek RTL8187SE (with the drivers that came with Windows 7)

These older devices are known to be incompatible:

Intel 3945/4965/5100
Realtek RTL8187 (like in older 802.11bg USB dongles)
Zydas ZD1211 (also in 802.11bg USB dongles)

Anyone managed to make it work?