Problem with assembly signing

Hello Experts, i'm new to C# programming and to this site, so please execuse my stupidity!

When I try to build my solution I get the following error:

The type or namespace name "WinForms" does not exist in the class or namespace "System" (are you missing an assembly reference.)

I think this has something to do with assembly signing but I'm not very sure. I also have the following assemblyInfo file that I got from someone and I really think the assembly needs some signing or something........it mentions the key that is installed in the Crypto Service Provider on my machine........i can't get what I am required to do. What do you advice????


AssemblyInfo.cs


using System.Reflection;
using System.Runtime.CompilerServices;

//
// General Information about an assembly is controlled through the following
// set of attributes. Change these attribute values to modify the information
// associated with an assembly.
//
[assembly: AssemblyTitle("")]
[assembly: AssemblyDescription("")]
[assembly: AssemblyConfiguration("")]
[assembly: AssemblyCompany("")]
[assembly: AssemblyProduct("")]
[assembly: AssemblyCopyright("")]
[assembly: AssemblyTrademark("")]
[assembly: AssemblyCulture("")]            

//
// Version information for an assembly consists of the following four values:
//
//      Major Version
//      Minor Version
//      Revision
//      Build Number
//
// You can specify all the values or you can default the Revision and Build Numbers
// by using the '*' as shown below:

[assembly: AssemblyVersion("1.0.*")]

//
// In order to sign your assembly you must specify a key to use. Refer to the
// Microsoft .NET Framework documentation for more information on assembly signing.
//
// Use the attributes below to control which key is used for signing.
//
// Notes:
//   (*) If no key is specified - the assembly cannot be signed.
//   (*) KeyName refers to a key that has been installed in the Crypto Service
//       Provider (CSP) on your machine.
//   (*) If the key file and a key name attributes are both specified, the
//       following processing occurs:
//       (1) If the KeyName can be found in the CSP - that key is used.
//       (2) If the KeyName does not exist and the KeyFile does exist, the key
//           in the file is installed into the CSP and used.
//   (*) Delay Signing is an advanced option - see the Microsoft .NET Framework
//       documentation for more information on this.
//
[assembly: AssemblyDelaySign(false)]
[assembly: AssemblyKeyFile("")]
[assembly: AssemblyKeyName("")]