Troubleshooting Windows XP, Tweaks and Fixes for Windows XP:
"Registry Edits for Windows XP: 'Tweaks and Tips' "

How to run scheduled tasks without a password
If you're using XP Home, the easiest way to make this change is to download the VBScript file from Kelly's Korner. See line 67 at:

http://www.kellys-korner-xp.com/xp_tweaks.htm