Yes, you can open OLK file that too in multiples without having to change the extension. Install OLK Viewer freeware, select all, you need to read and load them on to the OLK viewer Freeware panel. You can easily view the messages along with their contents and attributes clearly displayed. NOTE: Making changes to the extension of any file can cause damage to its contents. Ensure that you create a copy of OLK files before making any such attempts.