"We'll use the transition from Ubuntu Hardy Heron to OpenSUSE
11.0 as an example, but the basic steps are the same with most
combinations of distros.
"The main drawback of a new installation is that it reformats
your filesystems, destroying whatever files were on them. That's
fine for the distro itself, but what about your personal files?
"The most important asset when switching from one distribution
to another is a separate partition for /home. Not only does it
prevent your personal files and settings from being destroyed when
you're installing a different distro, it also gives you somewhere
to save useful information, such as backups of system configuration