2003 Server uninstall problem

To find the objects with Exchange attributes, use the Active Directory Users & Computers snap-in.
 
1.  Run Active Directory Users & Computers.
2.  Right-click your domain at the top of the tree and click Find.
3.  Click the Advanced tab and then choose User from the Field button.
4.  From the list of attributes displayed, choose Exchange Home Server.
5.  Set the Condition field to Ends With and then type the name of your Exchange server into the Value field.  Click Add to add this value.
6.  Click the Find Now button which should now display the problematic objects.
 
The Exchange attributes can now be removed from these objects and the uninstall process attempted again.

http://support.microsoft.com/kb/555147