I'm no expert on this, but try the following.........
I can't remember what Control panel item I located this in, but go to Start > Run, and type optionalfeatures and hit Enter.
Scroll down until you see Web Management Tools and expand that tree. Problem is it only reveals II6, not II7. Look through all the various sections such as World Wide Web Services, Security. .NET Framework and possible Windows Product Activation Services.
I believe Windows 7 comes with .NET Framework 3.5 already installed by default.
You can check your version by going to c:\windows\Microsoft .NET.