my visual studio website won't compile after I reformatted my computer

I reformatted my computer.

I installed Visual Studio 2012 express

I attempted to compile a project that used to work, and I get:

Error 6 Type 'System.Web.UI.WebControls.HiddenField' does not have a public property named 'ClientIDMode'. 
Error 21 Type 'System.Web.UI.WebControls.GridView' does not have a public property named 'SortedDescendingHeaderStyle'.

I do know that these errors are simply incorrect.  Gridviews do have the so-called illegal property, and so do hidden fields.

I also see that when I create a totally NEW blank website, that I don't get these errors.  

In the new website, I tested the NET framework, and it was 4.0.30319.18052

What could be causing this?