Hi,
It looks like its the way office was originally installed - from an administrative installation point.
When a component of office needs updating due to office's "self healing" or some uninstalled component, it asks for data1.msi (if the component is on CD1)
See the following link for a description of this...
(remove spaces in the URL)
http://www.microsoft.com/office/ork/2000/two/30t2_1.htm
If the users dont have installer rights, then you're going to have to do it for them... Either they install or they dont... Thats the decision your business makes and will invariably involve extra work for support staff to do the installations.
But maybe not as much work as fixing THEIR botched and dodgy installations!!??!!
Cheers,
Tim.