Ok, this one had me stumped for a bit, and it took me a long time to find out why. Basically, the problem is that there is no ASP.NET tab in website properties, and this is because .NET isn't installed properly. The first thing to do is download and install .Net framework, which dosn't seem to do anything.

The second thing to then do is to run: %SYSTEMROOT%\MICROSOFT.NET\Framework64\v2.??\aspnet_iisreg -i which will then try and re-register. Now if this "works" but dosnt have any effect, its probably because you've got a beta of .Net installed. However, if this throws an error, its probably because IIS is running in 32bit mode.

Why would it be? Well aparantly it has to to be able to deal with PHP. Maybe thats true, maybe it isn't any more - but either way, theres lots of install guides out there telling you how to break it into 32 bit mode. To Fix...

cscript %SystemDrive%\inetpub\AdminScripts\adsutil.vbs set w3svc/AppPools/Enable32bitAppOnWin64 0

The 0 is what sets it back to default (64 bit) where having that as a 1 will set it to being 32 bit mode. Of course now all your PHP is probably broken. But then again it was anyways.

Just re-run the first command, and reboot (IIS? Server?)