Before opening any of the application hold down CTRL.
Office 2003 works abosultely fine on Windows Vista however, not if have Office 2007 installed along side it. Regardless of what version of Office 2007 it is whatever you may come across a MAPI32.DLL error when using Outlook 2003 and even uninstalling Office 2007 will not work.
To solve the problem is simple, locate the file MSMAPI32.dll here:
C:\Program Files\Common Files\System\Msmapi\1033
and either delete it or best practice, rename it to MSMAPI32.dll.old