If you want to upgrade from CentOS 6.0 or 6.1, all you need to do is run “yum update” as root, and then reboot. The reboot is required because the kernel is updated.
If you have CentOS 5.x or 4.x, then there is no path for you to update. For the adventurous, you can certainly get it to work, but you’ll be in for some pain. Check the release notes for some ideas on where to start: http://wiki.centos.org/Manuals/ReleaseNotes/CentOS6.2
The new installer in the 6.x release is a little easier to use, and the boot times are certainly much better.
If you use netinstall, then the URL containing the centos installation image for 64bit is:
And if for some crazy reason you are still using 32bit:
I’m a little at a loss as to why these URL’s aren’t in the installer by default.