How to solve Handler "PageHandlerFactory-Integrated" has a bad module "ManagedPipelineHandler" in its module list in IIS

Fresh install of the OS and Visual Studio and I am trying to run a .Net 4.0 Application. I was able to deploy through Visual Studio 2010 using IIS, but when I went to run I would get the error:

HTTP Error 500.21 - Internal Server Error

Handler "PageHandlerFactory-Integrated" has a bad module "ManagedPipelineHandler" in its module list

Detailed Error Information

Module	IIS Web Core
Notification	ExecuteRequestHandler
Handler	PageHandlerFactory-Integrated
Error Code	0x8007000d

Requested URL	http://localhost:80/app/default.aspx
Physical Path	C:\inetpub\wwwroot\app\default.aspx
Logon Method	Anonymous
Logon User	Anonymous

Most likely causes:

• Managed handler is used; however, ASP.NET is not installed or is not installed completely.
• There is a typographical error in the configuration for the handler module list.

Things you can try:

• Install ASP.NET if you are using managed handler.
• Ensure that the handler module's name is specified correctly. Module names are case-sensitive and use the format modules="StaticFileModule,DefaultDocumentModule,DirectoryListingModule".

Links and More Information

IIS core does not recognize the module. View more information »

So on a hunch and dealing so much with IIS and ASP.net issues, I decided to reinstall ASP.Net using the command line. Run the command line as admin and type the following:

%windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_regiis.exe -i

This will reinstall ASP.NET. This should solve your error as it fixed mine