Question : System.Core

------ Build started: Project: ManifestManagerUtility, Configuration: Debug Any CPU ------
C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Microsoft.Common.targets : warning MSB3245: Could not resolve this reference. Could not locate the assembly "System.Core". Check to make sure the assembly exists on disk. If this reference is required by your code, you may get compilation errors.
c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Csc.exe /noconfig /nowarn:1701,1702 /errorreport:prompt /warn:4 /define:DEBUG;TRACE /reference:c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Microsoft.Build.Tasks.dll /reference:c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Data.dll /reference:c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Deployment.dll /reference:c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.dll /reference:c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Drawing.dll /reference:c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Windows.Forms.dll /reference:c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Xml.dll /debug+ /debug:full /optimize- /out:obj\Debug\ManifestManagerUtility.exe /resource:obj\Debug\ManifestManagerUtility.AboutForm.resources /resource:obj\Debug\ManifestManagerUtility.MainForm.resources /resource:obj\Debug\ManifestManagerUtility.ManifestSigningDialog.resources /resource:obj\Debug\ManifestManagerUtility.Properties.Resources.resources /target:winexe ..\..\GlobalAssemblyInfo.cs AboutForm.cs AboutForm.Designer.cs ApplicationFile.cs MainForm.cs MainForm.Designer.cs ManifestHelper.cs ManifestSigningDialog.cs ManifestSigningDialog.designer.cs Program.cs Properties\AssemblyInfo.cs Properties\Resources.Designer.cs Properties\Settings.Designer.cs
error CS1504: Source file 'C:\Documents and Settings\mxcupryk\Desktop\ManifestManagerUtility\GlobalAssemblyInfo.cs' could not be opened ('The system cannot find the file specified. ')

Compile complete -- 1 errors, 0 warnings
Done building project "ManifestManagerUtility.csproj" -- FAILED.
========== Build: 0 succeeded or up-to-date, 1 failed, 0 skipped ==========

I am using asp.net 2.0?

Answer : System.Core

Try a few simple solutions to attempt to rectify the problem:

1. Clean the solution and rebuild.
2. Ensure the assembly is registered in the GAC. C:\Windows\assembly
3. Reinstall the .NET 2.0 framework. http://www.microsoft.com/downloads/details.aspx?familyid=0856eacb-4362-4b0d-8edd-aab15c5e04f5&displaylang=en

Hope this helps!