I was installing Sitecore tonight on a fresh install of Windows and ran into this old error:
HTTP Error 500.21 - Internal Server Error Handler "PageHandlerFactory-Integrated" has a bad module "ManagedPipelineHandler" in its module list
It wasn’t the first time I’ve seen this error, but I always shave to look it up when I run into it because I hadn’t committed the solution to memory.
A quick Google and a visit to Stack Overflow got me the answer I needed. It was because ASP.Net had not been installed into IIS, and that is pretty easy to fix. Just open up command prompt with admin privileges and run the following command:
"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe" -i
You should then see the following on the screen:
Microsoft (R) ASP.NET RegIIS version 4.0.30319.0 Administration utility to install and uninstall ASP.NET on the local machine. Copyright (C) Microsoft Corporation. All rights reserved. Start installing ASP.NET (4.0.30319.0). ..... Finished installing ASP.NET (4.0.30319.0).
At that point you can close command prompt and then go back to your web browser and refresh the page. It should load without issue!