Disk Defragmenter
Command Line Kung Fu
I was trying to figure out how to run Disk Defragmenter from the command line on a SBS2003 box as I was not sure how to specify what drive I want defrag.exe to run on at a specific time. Turns out that you can just browse to defrag.exe (…/system32) and then tell it what drive to run on in the advanced properties of the Task Scheduler. Microsoft has a write-up on the whole process.
A better otpion is to use a fully automatic defragmenter like Diskeeper 2009 that is install-and-forget. It automatically defrags all the drives in the background, as required, and there is no need to schedule defrags or waste time defragging manually.