Check your .Net framework location , usually is
C:\Windows\Microsoft.NET\Framework\v4.0.30319
you can put this in a batch file ( “iisreg_fx4.bat” ):
REM "Changing to the Framework install directory"
cd /d C:\Windows\Microsoft.NET\Framework\v4.0.30319
echo "Stopping IIS"
iisreset /stop
rem regiis
aspnet_regiis -i
echo "Restarting IIS"
iisreset /start
echo "----------------------"
pause