You can use the program Autodefrag found here and schedule the task as posted here:
Originally posted here by Maestr0
The simplest way to do this (using NetBIOS) is to open the remote machine and schedule a task by opening the Scheduled Tasks folder (you must have remote registry enabled for this). The other simplest way is to use the 'psexec' tool from sysinternals or something similar.

http://www.sysinternals.com/ntw2k/freeware/psexec.shtml
-Maestr0