Solution 1:

Take a look at Connectify: http://connectify.me

Solution 2:

A detailed step-by-step to setup wifi tethering/hotspot in Windows 7, Windows 8 WITHOUT any 3rd party software:

  1. From admin Command Prompt type:

    netsh wlan set hostednetwork mode=allow ssid=mywifinetwork key=mysecretkey
    
  2. Enable new virtual Wi-Fi adapter (it might be disabled upon creation)

  3. From admin command prompt type:

    netsh wlan start hostednetwork
    
  4. From current internet conection adapter share (ICS) internet to the new virtual adapter

  5. Connect from wireless client to virtual SSID. Wi-Fi client gets an auto IP and you're good to go.

After host computer restart you only need to repeat steps 3 & 5 to be up and running.