scheduling Disk Defragmenter in Win2000

The task scheduler in Win98 allowed one to schedule Disk Defragmenter to run at a particular time.

After upgrading to Win2000 (from NT), I tried to use Task Scheduler to defrag, choosing the program to run from:
C:\wint\System32\dfrg.msc

Unfortunately, task scheduler only launches the defragger application, ie the defrag program just sits idle, ie doesn’t start defragging!!

Is there any switch that causes the program to start defragging automatically ? Or how can I schedule it to actually *run* ?!