Task manager does not open after deleting Process Explorer

I've installed Process explorer on my Windows 8 64 bit system. Few days later I have removed Process explorer again but the standard Task Manager won't open any more. How to fix this?

You have selected that Process Explorer should replace Taskmanager.

Delete the taskmgr.exe key in the registry under

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\

Now You will be able to run Taskmanager again.

1) Go to start menu and open "regedit"

2) Go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution\taskmgr.exe\

3) Delete the value inside "Debugger"

NOTE: The "debugger" key open program that replace the default task manager"