So long story short, to switch my individual site over to ASP.net 4.0 I had to use aspnet_regiis to manually set the framework version for that one site. Here's how:
- First we have to find the website iis path. Go into IIS, under the website properties under the "Website" tab there is the Logging section. Click on and right click on the "Properties" button. This will bring up the "Logging Properties" dialog which lists the name of the website at the bottom next to "Log file name" eg. W3SVCXXXX. Make a note of this.
- Open a command prompt to the c:\windows\Microsoft.net\Framework\v4.0.30319\ folder of your choice. (v2.x, or v4.x)
- Run aspnet_regiis -lk (that's -LK) this will list the websites and their paths and what version they are running. Use the name you found in step 1 to get the full path.
- Run aspnet_regiis -s PATH, e.g. aspnet_regiis -s W3SVC/123456789/root/ where PATH is the path you found in step 3.
That's it, hope this helps you.