I found a blog post pointing to an easy way to automate defrag in windows xp. This is extremely easy to do and is something that more people should definitely do because it will help their Windows computers run much faster.

The steps are basically as follows

1. open up task scheduler
2. put in %systemroot%\system32\defrag.exe %homedrive% as the command
3. select a time for defrag to run every night.

Here is the post