regtool.exe is an executable file, which is related to RegTool MFC Application also known as RegTool. This program is labeled as potentially unwanted program or a fake registry cleaner that notifies about questionable registry errors and fails to remove them. For that you will have to buy its licensed version. Please, do NOT pay for RegTool's license because it has no ability to fix all registry errors and improve computer's speed. It's just another scareware, which is used for making money.
Just like any other executable file, regtool.exe is responsible for starting a program or launching some of its components. Once executed, this process may also start monitoring parasite's payload or working on its own.
To sum up, regtool.exe is a dangerous process that is related to suspicious program. If you noticed this process running on your PC system, you should terminate it and remove its components. For that we recommend using RegCure Pro.