I am using turbo tax 2007 business to file my company taxes for tax year 2007.
How can I use this same version to file my previous years for 2006 and 2005 tax years?

Hi, lfleary!

I know that your question is somewhat dated now, but I thought that I would place it in a more appropriate topic area so that it might get noticed more and answered the best because of the persons who usually frequent this topic area.

Thanks!

I am using turbo tax 2007 business to file my company taxes for tax year 2007.
How can I use this same version to file my previous years for 2006 and 2005 tax years?

For 2005, you need Turbo Tax 2005. For 2006, you need Turbo Tax 2006.

Also you may have difficulty in completing all the required returns for a year, yourself. First try 2007 (you have turbo tax) and see if you can do it. For federal you will complete Form 1120 or 1120s (if S corp), then franchise tax return for the state, then return where the corp is registered.
May be you should contact a CPA.