Get this type of thing a lot at work... DAT (and CSV and various other extensions) are not actually file types, but general purpose extensions used by many different applications. Therefore, you need to know what application your particular DAT file is for. Couple of things you could try: - see if it is simply plain text, by attempting to open it from NotePad or WordPad - see if it is simply compressed by unzipping it using whatever zip tool you have on your PC... then open the unzipped file(s) using NotePad/WordPad - failing that, it will be safe to assume it is a binary file... there are many free tools that attempt to open and interpret binary files (its at that point I would normally bounce it back to the client and get them to provide the file's definition, as it could literally be ANYTHING!)
When you list file , select it then right click and select 'open with' and select Notepad . As other post it may simply be code which you then need to analyse with an app or similar Or open into excel using import function setting the breaks to organise the date logically
