I have completed my project to script the conversion of 2003 files. Office Convert.zip contains scripts to convert Word and Excel 2003 files to 2007. The scripts call touch.exe, a utility that allows me to set the new files with the same filestamp data as the originals. It can be downloaded from http://www.codeproject.com/KB/applications/touch_win.aspx.
The scripts can be run interactively or from the command line. Examples are in the ZIP.