The .NET Framework cleanup tool automatically removes selected versions of the .NET Framework from a computer. It will remove files, directories, registry keys and values and Windows Installer product registration information for the .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, uninstallation, repair or patching errors so that you can try to install again.
The .NET Framework setup verification tool automatically verifies the installation state of one or more versions of the .NET Framework on a computer. It will verify the presence of files, directories, registry keys and values for the .NET Framework. It will also verify that applications which use the .NET Framework can be run correctly.
Both are free tools written by Aaron Stebner and recently updated to support .NET v4.