IPv6 is the next generation Internet Protocol which will eventually replace IPv4. Microsoft has implemented IPv6 in Windows many years ago and it is enabled by default in Windows 7 and Windows 2008. Not many organizations have implemented IPv6 networks and thus have no use of running their workstations and servers with an IPv6 interface enabled.

There are three ways to disable IPv6 in Windows 7 and Windows 2008

Method 1:
To disable IPv6 on Windows 7 and Windows 2008 using the GUI go to Properties of the network interface in Network Connections folder and uncheck Internet Protocol Version 6.

Method 2

Click Start and type Regedit.exe and click Regedit. When prompted click continue in the UAC dialogue box. Navigate to the below registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\
On the right pane right-click and create a new DWORD (32-bit) value.
Type DisabledComponents and hit Enter
Double-click DisabledComponents and type 0xffffffff and click OK.
Restart the server/workstation.
IPv6 is now disabled.

Method 3

The fastest way for those who love the commandline is to run the following command and reboot. Make sure to run CMD as Administrator.