Hi bschoolm,
One approach is to keep the database of locations in a non-Streets & Trips file, such as Excel, from which it can be at any time imported to any S&T version. However, if your client only has the locations in an S&T file, they could try to open
on the same computer an instance of S&T2003 and an instance of the latest version, then copy/paste pushpin sets from old to new. If that approach is not possible, you could try the steps described at the following URL: http://www.laptopgpsworld.com/4341-microsoft-streets-trips-2011-unable-open-map-saved-much-earlier-version
Laptop GPS World