iIS 7.5 error: HTTP Error 500.21 - Internal Server Error Handler PageHandlerFactory-Integrated has a bad module ManagedPipelineHandler in its module list

if you found the following error on IIS 7.5 while opening asp.net 4.0 application

iIS 7.5 error: HTTP Error 500.21 - Internal Server Error Handler “PageHandlerFactory-Integrated” has a bad module “ManagedPipelineHandler” in its module list

then run these commands to install asp.net 4.0 to fix the issue

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

%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe -i