Another way is first to backup the old entire directories in previous VSS, then after installation of the new one, restore the backup .ssa file to the new empty database.
how? first use VSS explorer then in File-----> open source safe databse------> browse to the new database location and open it. then open VDD admin and restore the backup job, choose another location instead of the Original location and point to new $ database. after restore open the VSS explorer on each client computer open the new databse, choose each project and create for each a new working folder. attention that no project is still have the old working folder. after a while when you are sure that all changes are transferred to the new VSS, you can delete the old working folders.
hope this helps