as in my case, the option is under Sharing tab in Properties (right click >> Properties) for the mobile broadband network.

as i remembered, there's a check box under the Sharing tab that you need to tick to enable the internet connection sharing, and there's also a drop-down menu that allows u to select which network that u're going to share that network with, as is in this case select the Wireless Network. (I don't remember the exact one, can't check now coz @office.. PC here got disabled the settings by system admin. need to get back home to my laptop confirm)

for the mentioned disable/enable internet sharing, simply tick/untick the checkbox

correction:

in my case, i'm sharing my mobile broadband internet on my laptop with my handphone via wifi..

- in Network Connections, right click on the network which is the mobile broadband network, and select Properties.
- under the Advanced tab, there's a column for Internet Connection Sharing, just tick the checkbox that says "Allow other network users to connect through this computer's Internet connection" and select "Wireless Network Connection" under the Home Networking Connection.
- click on Settings, which on the bottom right side of the Internet Connection Sharing column, and tick all the checkboxes for "Services", and select OK once done.
- click OK again to apply all the settings.
- done!

please note that the steps mentioned above is for XP.. not sure about Vista @ 7

got any one using smart movie?