The zip file that is created during a manual backup is: Act!+databasename.zip I suggest that the Act! version number be added to the backup file name, or using the same naming as Act! Scheduler does.
A customer of mine recently did a manual backup, installed Act! v19 and did a new backup, overwriting his old backup, got problem with the installation and installed his old version of Act! just to find that the backup contained the v19 database and not his old one.