I had a request for this today , so I thought I would plop it on my blog.
I set this for all of my workstations, to run a daily defrag.
The following command will set a daily defrag to start the given date & time, feel free to change the dates and times.
schtasks.exe /create /SC DAILY /TN fragme /TR ""C:windowssystem32defrag.exe"c: -f" /ST 00:45:00 /SD 03/04/2008 /RU SYSTEM
Copy the following, and put it in a .CMD or .BAT file and your set.
This will make a scheduled task.