This error seems to pop up every now and again when I configure a new IIS server, even if I do remember to check the ASP option during the initial role selection.
Here’s how to resolve it (run as admin) on a 64-bit system:
%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe -i
..and on a 32-bit system:
%windir%\Microsoft.NET\Framework\v4.0.21006\aspnet_regiis.exe -i