The DAT files can't be used without an application and as far as I know, you need something that understands their structure. In DAT files you can store audio, video, graphic content, text, databases etc. There you should install the support software for DAT files that you work with and then you will be able to open them. I've just downloaded a sample DAT file and I couldn't open unless I've used an application that "understands" the content.