Problems recognising second debian sarge CD

["Rich" <hillhead@btinternet.com>]

We've been having a go at installing Sarge.
We have got the base system installed OK but have come up against a problem
when trying to install the remaining packages.
The installer (base-config) asks us to insert the second CD

Debian GNU/Linux testing _Sarge_ - Official Snapshot 1386 Binary-2
(20040417)

When I do so, it doesn't recognise it! The CD isn't damaged in any way, and
nor is the image. We burned a new disk, same result.
Do I need to actually title the disk 'Debian GNU/Linux testing _Sarge_ -
Official Snapshot 1386 Binary-2 (20040417)' when I burn it?
It's all I can think of, but nowhere did I see any instructions telling me
to do so.
(I downloaded the images using Jigdo from the official site and burned them
as bootable ISOs)

This one's kinda got me stumped.