I've installed some weeks ago Ubuntu 11.10 from amd64 DVD version
Now I've got the 12.04 amd64 CDROM version.

I booted with this 12.04 version and after some time, I got the upgrading option disabled (cannot select it). Also, when I boot 11.10 and insert the 12.04 CDROM I don't get the upgrading message as usual.

Should I download the 12.04 DVD-amd64 version to do the upgrading?

Thanks a lot in advance,