Why ohhh why did Micr$oft decide to remove the ability to create an adhoc network through the network sharing center GUI ??????? Are they mad!!! Now if you want to create an adhoc (computer to computer) wireless network you have to enter the following commands:
[*] netsh wlan set hostednetwork mode=allow ssid=<enter_network_name_here> key=<enter_password_here>
[*] netsh wlan start hostednetwork
I honestly cant believe that they would remove functionality ??????
Source : LINK