The tool "Reset Environment" enables users to quickly reset the working environment without the downsides of other approaches to do so.
For instance, by modifying the environment not via System => Advanced system settings => Environment Variables, but with tools like the Registry Editor, "O&O RegEditor" from www.oo-software.com or "Registry Workshop" from www.torchsoft.com the changes do not immediately come into force. As a result, a new command line does not contain the modified settings.
Alternatively, one can kill the explorer.exe via Task Manager and start the explorer.exe again by File => Execute => Explorer.exe. However, doing it that way is tedious.
On the other hand you can send a message to all top level windows including explorer.exe programmatically by "SendMessage ( HWND_BROADCAST, ... )". Because explorer.exe is the one spawning new processes, the new settings are now available to the children. That message sending is done by the ResetEnvironment.exe contained in the zip file or the setups of the downloads below.