Windows 2000 Default Printer Varies

I’m have a windows 2000 user that is experiencing an unselected change in their default printer. For example, the user worked late printing from Excel to a local printer. Logs in early the next morning, opens the same file they were working on andprints finding that the default printer is now a network printer in another office. Due to sensitive material, no other person had access to
this users system or acount. Any ideas?