From the Readme…
Opening an old file in ACA 2008 can appear to hang up your system.
When previous version drawings are opened, a dialog is displayed with a warning that saving this drawing will upgrade AEC objects to 2007 format. If a previous version drawing is opened by double-clicking the file in Windows Explorer, this dialog may be hidden behind the drawing making AutoCAD Architecture 2008 appear to have hung; clicking anywhere on the application to give it focus will make the dialog come to the foreground.
The promotion of previous version drawings to 2007 format can be automated through the use of a batch process, which starts with the creation of a batch (bat) file. Running the batch file makes a complete copy of the project (or folder that contains previous version drawings), then recursively searches for all dwg, dwt and dws files contained in this location and finally generates a script (scr) file. Running the script file results in each of the copied dwg and dwt files being opened, saved and closed, which results in these files being promoted to 2007 format. If any dws files are contained in the designated folder, their paths are displayed. These files will need to be manually opened and saved in 2007 format.
The full text of the procedure is in the Readme file in your ACA 2008 product.