Can someone tell me if (and where) I can get a copy of the previous version of ServiceDesk?

Our installation has died and I downloaded 8.2 and installed it on a new machine but when I try to restore the backup into it I see the process running but at the end I still seem to have a blank (new) copy of ServiceDesk,  Looking back through the DOS box that runs for the restore I see a message saying "Backup build number not compatible with existing build"

From that I assume I need to install the older version again to restore the database.

Thanks very much :)

Chris