I should have been a little more clear - that message will pop up when you attempt to use a feature or component of Office that was not initiallly installed on the client.
Office being the behemoth that it is, the initial Office install lets you set up certain seldom-used features & components to be 'installed on first use' as a way of conserving drive space on the client, or simply flagging them as not installed & not available. There is a third option - 'run from CD' - but I'd expect very few people to use that.
When the user of a client machine attempts to use an uninstalled feature or component that was flagged 'install on first use', Office will attempt to retrieve & install the feature using the source path of the initial installation & will proceed with the install if it finds it - if that source path is unavailable, you get that prompt. If you have the discs, you can try browsing to the pro.msi file on the CD within that dialog, even though it was a network install, and it will probably proceed. I say 'probably' only because I haven't used Office XP - my experience is only with Office2K & God knows what additional hurdles MS has built into subsequent versions.
Hope that's a little more understandable.
Cheers,
Daiwa
