There are four buttons at the bottom of the dtpower window:
Apply puts into effect all of the settings currently displayed in the window.
Reset changes all of the settings back to the state they were in when Apply was previously selected (or to default values if this is the first time you have run dtpower). Reset, however, will not return to earlier values if you have already selected Apply.
Quit dismisses the dtpower window; no icon remains on the screen. Any setting that was not put into effect with the Apply button is lost.
You can reduce this dtpower window to an icon on your desktop.