Yast installation media problem

I did my original installation of SuSE 9.1 Pro using CDs, but now I want to switch over to the DVD. I changed the installation medium within Yast, specifying DVD, and indeed, the URL for the chosen source is "dvd:///". When I attempt to install a new package, Yast is able to find it. But when it gets to the stage of actually installing it, I get the message: "Insert SUSE LINUX Version 9.1 DVD 5" Presumably the package I want is actually on CD 5. Inserting the (single) DVD does not satisfy the request. How can I get past this? Paul Abrahams