One solution for running PC software on the Mac is
CrossOver - it is based on the Linux WINE app and allows you to build "bottles" with a single Windows app in each (no Windows key needed).
So, I decided to test this on my Mac and see if it would be a feasible alternative to Parallels (it works fine but the virtual PC takes 6GB of space).
I created a "bottle" and inserted the Microsoft Streets and Trips 2008 CD, it goes through up to where it tried to install the text to speech features. It barfed and aborted the installation, leaving me with a non-usable "bottle".
Looking at the compatibility center on the CrossOver site, Streets & Trips versions 2001, 2004, 2005, and 2008 were listed as "untested" and 2006 and 2007 were flagged as "Known not to work", and I guess 2008 should be moved to the latter category too.
So, there you have it. It's better for Mac users to use Parallels or VMWare Fusion if they want to use Streets & Trips on the Mac.