How To Add ASP.NET 4.0 As Application Pool On IIS
Here we consider How To Add ASP.NET 4.0 As Application Pool On IIS.
First of all, install .Net Framework 4.0 in your System.
You can install .Net Framework 4.0 from here Install .Net Framework 4.0.
After installing .Net Framework 4.0 on your System, install IIS as follows.
Install IIS Reference : - Install IIS on your System.
After installing IIS, navigate to List of Application Pool inside IIS.
Check whether ASP.NET 4.0 is listed or not?.
If not, Run Command Prompt Window in Administrator mode.
Type cd C:\Windows\Microsoft.NET\Framework\ v4.0.30319\ and Press Enter.
Then type aspnet_regiis.exe -ir and Press Enter.
This will register ASP.NET 4.0 Application Pool to IIS.
Close everything and Open IIS again.
Now you can see ASP.NET 4.0 is listed in the list of Application Pool.
For Selecting ASP.NET 4.0 for your Application follow these steps.

Open IIS. Now Right Click on your Website and select Manage WebSite
Then select Advanced Settings. Here you can find the settings for that website.
On the General Section, note down the name of the Application Pool.
For Adding Application Pool, click on the Browse button on Application Pool section.
This will list all Application Pool. Here select ASP.NET 4.0 and press OK.
These much of steps will Add ASP.NET 4.0 Application Pool to your website.