Here's how to keep Task Manager running but hidden from view. That's a nice way to set it up, in my opinion.
First open it by pressing [Ctrl][Shift][Esc]. Now choose Options >> Hide When Minimized.
Minimize Task Manager. Its icon will appear in the taskbar in the System Tray -- next to the clock in the lower right corner. To make Task Manager visible, double-click its icon. After each use, minimize it again. Don't close it.