Actually, one has to understand how the software works and how it create its own file. Apparently, there is only one SanDiskSecureAccess Vault per drive—USB drive contains three folders and one application—that has many .dat files. There is a Backup and Restore function built in the application program.
To be honest, I have not used the backup function since I assumed that copy/paste to a Windows PC folder would suffice before I updated from “SanDiskSecureAccessV2_win” to a new version “SanDiskSecureAccessV3_win,” which does ask for a new password because it created a new Vault. That is why you will not see the files contained in the new vault until you move/save files into it. However, I do not know if the software saves the old vault file from the SanDiskSecureAccessV2_win version. If you formatted the USB drive prior to updating to the new version, then the files are lost. If you have not formatted the drive other than updated to the new version, the files are still on the drive, which you will need to run a recovery program to retrieve the .dat files.
In closing, it is best to read the user guide, customer reviews, SanDisk forum before making any changes/updates. If you do not trust the SecureAccess, you can always use a free encryption program called “SafeHouse Explorer” where you can create as many volumes as you desire. I can move any SafeHouse volume file from USB drive to Windows PC anytime and still be able to open the volume using the SafeHouse Explorer app. It would certainly be easier if SanDisk Secure Access were created in a similar fashion.