Fxcop.exe – .NET Framework Initialization Error

FxCop is an application that analyzes the assemblies of managed code (code that directs the .NET Framework common language runtime) and information about the assemblies, such as potential design improvements, localization, performance, and security.
For two days, I am getting this error while trying to run fxcop.exe.
The screenshot of the error is

Fxcop.exe – .NET Framework Initialization Error
Unable to find a version of the runtime to run this application.
I'm not sure about the cause as no ran with frequency. Last I used it while working on a project for a month. Now I need to re-run it, but now I'm getting the error mentioned.
I am using Windows XP SP2, visual studio 2008 and .net framework 4.0 . The hardware in my PC is Core i3 processor with 2 GB of ram.
