There is no way to do this in Outlook 2000.
As workarounds, you can try:
1. Create custom folders for those tasks that have subtasks and try to keep them fairly organized that way.
2. Create a category for tasks that have subtasks, and assignall pertinent tasks to this category. View your tasks by category and, voila, you've got each subtask listed under its own little heading. If helpful headings like "status" and "due date" aren't available, use the field chooser to drag-and-drop theminto your view. Then you can just go down the list of tasks completing them as you go.
Hope this helps!
WetMosaic (wetmosaic@angelfire.com)
Brainbench MVP for Windows Fundamentals
http://www.brainbench.com