Problem with Microsoft Outlook

I recently upgraded a pc for a person using Microsoft office outlook for email and calendar. (upgraded Windows 2000 to Windows XP Pro) I upgraded him to office XP realized it was doing some strange things even after I imported his data. Tried to go backwards (I know not the best thing to do but it was my only solution, I uninstalled all office packages including outlook 2003). I reinstalled Microsoft Outlook in Office 2000, which is where he originally started and it just hangs. Any suggestions?