How rolling back DAT files works
If you find your current DAT files are corrupted or incompatible, you can roll back the DAT files to the last backed up version.
When you update DAT files, the old version is stored in this location: <drive>:\Program Files\Common Files\McAfee\Engine\OldDats.
When you rollback the DAT files, the current DAT files are replaced with the version in the OldDats folder, and a flag is set in the registry at this location: HKEY_LOCAL_MACHINE\SOFTWARE\McAfee\DesktopProtection\szRolledbackDATS.
Once the rollback occurs, you cannot go back to the previous version again. The next time an update occurs, the DAT version in the registry is compared with the DAT files in the update repository. If the new DAT files are the same as those in the registry, no update occurs.