You need Domino (iNotes or QuickPlace) to show dates in dd/mm/yyyy format on Windows NT/2000, you've changed the Regional Settings and the Locale to something other than "United States" and restarted the computer, yet the format is still wrong. There is a registry setting that seems to over-ride your regional settings that Domino picks up on, here's how to fix this.
If you are happy to edit the registry (standard "backing up first" recommendation applies!) first go and have a look at "HKEY_CURRENT_USER\Control Panel\International" and you will see the 'Regional Settings' that you have applied, yet for some reason Domino doesn't seem to be picking up on.
Now go and look at "HKEY_USERS.DEFAULT\Control Panel\International" and you will probably see that the Locale is "United States" and the date format is MM/d/yy (or thereabouts). Change the settings in here to match those in "HKEY_CURRENT_USER\Control Panel\International", do a restart and hey presto, the format is as required.
Disclaimer: I've only ever done this on NT/2000 servers that only run Domino, so you may want to check whether this will effect any other applications that you may be using the server for.