The [CentOS] x86_64 DVD set is now spread over 2 DVD isos, while the i386 DVD remains as 1 iso file. We’ve had to split the x86_64 dvd media over multiple disks due to the increase in the binary packages size. We have, however, tried to build them in a way that dvd#1 should be all that is needed by most people. x86_64 DVD#2 is limited to some OpenOffice.org language packages.
x86_64 DVD#1 includes the rest of the distro and also includes the most popular OpenOffice.org language packs. More details on the exact split are available in the Release Notes.