If you are getting this error, the most likely cause is that you do not have IIS 7 installed on your computer.\
Here are the steps involved to install IIS 7 on Windows 8.1
Click on the start menu and type Control Panel. When the choices come up choose Control Panel
Click on Programs
Click on Internet Information Service and click OK
Windows will apply the changes. Windows will tell you when its complete. Click Close on the dialog.
You should now be able to reference the Microsoft.Web.Administration.dll
If you are getting started with IIS 7 and would like assistance getting started check out the ASP.NET IIS 7 QuickStart.
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