Did you create your new workgroup using WRKGADM.EXE? If so, then it joined you to that workgroup.
All you need to do it open WRKGADM.EXE and join "system.mdw" - then your unsecured databases will use that workgroup. To get into the secured database, use a shortcut to point you to the correct .mdw file. Here's an example I use to open a database including my workgroup file, user name, and password (with the good stuff XXXX'd out, of course):
"C:\Program Files\Microsoft Office\Office\msaccess.exe" "N:\New Database\New Database" /WRKGRP "n:\new database\PRODUCTION.MDW" /USER "XXXXX" /PWD "XXXXX"
Substitute your names in place of mine, and it should work.