How to Run Lion and Snow Leopard on Same Mac

If you want to run Lion without giving up Snow Leopard, create a new partition, install Lion on second partition, and then dual boot as needed. Lion takes away Rosetta which is a emulator that runs older Mac applications (like Office 2004) that you may want to continue using. Thanks to C|Net for this link.

http://reviews.cnet.com/8301-13727_7-20081187-263/how-to-keep-snow-leopard-when-upgrading-to-lion/