Last week, while setting up a backup solution for a customer, I learned something interesting about the Windows XP Job Scheduler:

It will not run a scheduled job if the user has a blank password.

Yeah, I know, you shouldn't have a blank password anyway, but some people just don't want to fool around with passwords on a 3-workstation peer-to-peer network.

So, you have three options:

1) Create an Administrator-level account with a password on the workstation and supply that user's credentials when saving the backup job.

2) Set a password for the normal user and supply that's user's credentials when saving the backup job.

3) Check the box labeled: Only run job if user is logged on ( or something like that ).  Of course, if this box is checked, the user can't log off their workstation when they leave for the day, creating yet another security situation.

So, after all is said and done, option 1 would be your best choice to circumvent the situation.