I'm running Ubuntu 6.06 and trying to upgrade to 7.04. (I know, I know, 7.10 is coming out in 4 days. This is sort of an educational exercise.) I have burned a CD after getting the ISO from the Ubuntu website. The MD5 hack for the ISO matched when I checked it. When I try to run package manager I eventually get the error seen in the screenshot. What's up?

Hmm. Evidently I'm not allowed to attach the screenshot.
So, the error reads:

E: Unable to correct missing packages

W: failed to fetch cdrom:[Ubuntu 7.04_Feisty Fawn_-Release i386
(20070415)]/pool/main/x/xorg-server/xserver-xorg-
core_1.2.0-3ubuntu8_i386.deb
MD5Sum mismatch

Believe your going to have to upgrade to 6.10 Edgy first. Then upgrade again to Feisty. When I went from 6.06 to 7.04 I just backed up my data and did a fresh install. Going to be somewhat of a pain whichever way you go.

And I just moved /home off to another partition, and installed Feisty fresh - in my case to a separate partition. I always use the alternate CD so I can assign (partition) mounts at install.
Found all my user data fine, and installed without problems.

I have a separate home partition so I upgraded from 7.04 to the 7.10 release candidate by booting the CD and formating the existing root and swap partitions. You might want to consider moving /home to another partition.

http://www.psychocats.net/ubuntu/separatehome