To verify if the .NET Framework 3.5.1 is installed even when it is not listed in the Windows 7 Control Panel, see the following instructions:
.NET Framework 3.5.1 is a Windows 7 component, but it doesn't populate in the list of names of installed programs in the Control Panel. A tool can be installed that will verify that it's installed and operating properly.
1) .NET Framework Setup Verification tool: https://blogs.msdn.microsoft.com/astebner/2008/10/13/net-framework-setup-verification-tool-users-guide/
2) Discussion group for .NET Framework installation issues: http://social.msdn.microsoft.com/Forums/vstudio/en-US/35d348e5-192e-4fa2-a45a-c1c2175ce111/net-framework-35-sp1-installation-problems-on-windows-7-x64?forum=netfxsetup
3) Blog on the verification tool containing links to download: http://blogs.msdn.com/b/astebner/archive/2008/10/13/8999004.aspx