Cant install Outlook 2003 over Outlook XP

[VIT]

Hi...We have a PC that has Office 2003 on it, but it still has Outlook XP.
We want to install Outlook 2003 but it says to uninstall Outlook XP first,
but outlook XP wont uninstall and we did this on another PC and when we tried
to remove Outlook XP, Outlook 2003 would still not install and we couldnt get
anything to work.
How can we install Outlook 2003 on tihs PC? That is the only office app
that is not Office 2003, all the rest are.

Thanks,
Russ