Here is a step-by-step guide to resolving this issue, ordered from the most likely to the least likely solutions.
For 99% of players, will solve "Unable to load library dbdatadll" instantly. For the remaining 1%, the permission and user account fixes will succeed. Here is a step-by-step guide to resolving this
To prevent the file from being deleted again immediately after you restore it or verify files, add the game folder to your antivirus exclusion list. Here is a step-by-step guide to resolving this