Stop installing Unwanted Programs in Windows 7 -Application lock

To enable Windows 7 AppLocker feature follow the steps below.
1.Click on Start
2. On search type gpedit.msc
Now press enter ,you can see the group policy editor on your computer.
3. Click on Windows Settings
Windows Settings present under Local Computer Policy.
4. Click on Security settings

5. Click on Application Control Policies
You can find AppLocker under Application Control Policies ,click on it.

Here you can configure the rules about the installing programs in your computer by clicking Configure Rule enforcement.
Supported OS for AppLocker
Note: AppLocker is available in all editions of Windows Server 2008 R2 and in Windows 7 Ultimate and Windows 7 Enterprise.