Installed it just today (WinXP sp3 eng). It's been defragging my sys disk for about an hour before I decided to explore the options window. After I clicked "Cancel" here's what I'm seeing. Heavy hdd activity is still there.
Now, what should I do if I don't want my data lost?
Hours later I know, perhaps you could have right-clicked on taskbar and brought up the taskmanager. Under applications tab, highlight Defraggler and select end task.