One additional word of caution.
Taking ownership has given you protection against standard users, but you should be aware that anyone with admin privilege can simply Take Ownership themselves, and access the files.
There are methods to truly protect these files but they are fraught with danger as you may end up locking everyone out from the files including yourself, (this involves removing all privilege from all users except your own user, but as you are a member of the administrators this can be problematic).
As long as you are the only administrator with access you should be safe but I would suggest you also backup the files regularly to a different location for full protection