The .NET Framework Setup Cleanup Utility is designed to automatically perform a set of steps to uninstall or remove selected old versions of the Microsoft .NET Framework from a Windows computer. It will remove files, directories, registry keys and values and Windows Installer product registration information for the .NET Framework.
Remove old .NET Framework
The tool is intended primarily to return your system to a known (relatively clean) state in case you are encountering .NET Framework installation, un-installation, repair or patching errors so that you can try to install again.
There are a couple of very important caveats that you should review before using this tool to remove any version of the .NET Framework from your system:
This tool will not remove the built-in .NET frameworks (3.5 version). It will only remove 4.0 and above on Windows 7.
This tool is designed as a last resort for cases where install, uninstall, repair or patch installation did not succeed for unusual reasons. It is not a substitute for the standard uninstall procedure. You should try the steps listed in this blog post before using this cleanup tool.
This cleanup tool will delete shared files and registry keys used by other versions of the .NET Framework. If you run the cleanup tool, you will need to perform a repair/reinstall for all other versions of the .NET Framework that are on your computer or they will not work correctly afterwards.
.NET Framework Setup Cleanup Utility download
Download & Details : MSDN.