To be brief - there is no easy way. There are ways to roll stuff back but in this case it will be much less painful to get a Hardy disk and reinstall.
A small piece of advice - keep your /home on a separate partition. That way, when installing a new distro/version, you can just mount that partition under /home without formatting and keep most of your settings intact. Although even here is a small pitfall
- due to distro customizations and/or updates in programs your settings from one distro can mess up things slightly in another. Usually easily solvable but you've been warned