Turn Windows features on or off is empty/blank in Windows 7/Vista

If you ever uninstalled a program in Windows Vista or 7 from the Control Panel, you probably noticed the option “Turn Windows features on or off” in the left pane of the window. This option allows you, just like for any programs you installed, to install/uninstall Windows features such as games, the indexing service, Internet Explorer, Windows Media Center and several other system components.

However you might have encountered a problem when you clicked the option and were faced with this window:

Usually you would see a "Please wait..." while Windows loads the features but here nothing happens, even after several minutes. This is a known bug that Microsoft acknowledges in their knowledge base article 931712 and although their proposed methods for fixing this bug might work for some people, it didn't for me.

What fixed it was actually enabling a service I had accidentally disabled in one of my sessions of fiddling with my system. The service in question was Windows Modules Installer, also known as Trusted Installer or TrustedInstaller.exe.

Here is how you activate it:

1. Go to Start > Run... or simply press Windows + R to open up the Run prompt window.

2. Type services.msc and press OK to open up the Services manager.

3. In the window that opens up, look for a service named Windows Modules Installer.

4. Double-click it, or right-click and select Properties.

5. In the window that opens up, in "Startup type:" set it to Automatic.

6. Press OK or Apply to validate.

Reboot your computer, everything should work as intended now.