Asp – IIS 6 Virtual directory MVC not working but Subdomain is

I get the following error when using MVC as a virtual directory

The value for the 'compilerVersion' attribute in the provider options must be 'v4.0' or later if you are compiling for version 4.0 or later of the .NET Framework. To compile this Web application for version 3.5 or earlier of the .NET Framework, remove the 'targetFramework' attribute from the element of the Web.config file.

at url
blah.domain.com/MVC

but at
blahmvc.domain.com

I get exactly what i want.

so i figured it was a configuration problem so I deleted the virtual directory
clicked on
blahmvc.domain.com and 'Save configuration to a File…'

and then on
blah.domain.com
new virtual directory from file
Read File
Location
Create A new virtual directory
Alias : MVC
and I get the same error when I try and go to the page

Using IIS6 and .NET 4.0.21006