Various programs nowadays are using the file extension .DAT to save data. Even when the following types of .DAT files are used widely, they can’t always be opened by a double mouse click.

Winmail.dat

The winmail.dat file is automatically created with Microsoft’s emailprogram ‘Outlook’, or the free version ‘Outlook Express’, and will be attached to outgoing emails. When this email is opened with Outlook, the program automatically recognizes the .dat attachment and the email will be shown fully intact.

If you however don’t have Outlook, you will need an extra program like ‘Fentun‘ to display the file properly. With Fentun an attachment like ‘winmail.dat’ can be opened to see the proper contents.

DAT video files

Another known form of DAT files are MPEG video in video CD format. These can be opened and played with mediaplayers like the free VLC player. The files only need the extension .DAT when they’re burned onto a video cd. When the file is put on a harddisk it can be renamed to .MPG, which is easier recognizable as videofile.