Just out of curiosity I asked my friend google about .dat files. Check out http://www.fileinfo.net/extension/dat for a general discription. Basically, a DAT file can be anything from a standard CSV (comma delimited data-file) to a proprietary binary file. From my own experience, I have seen .dat files (and .data files, used interchangeable) be used to store sets of class objects from specific applications, to images, to full in-house low-level databases. My guess is that yours is the third.

Hope this helps you understand why everyone wants to know where this file came from! Good luck!:)