A file ending in the DAT extension contains data for a specific program or document on a computer. DAT files are attached to so many types of files that it can be difficult to know what to do with it. A DAT file for a Microsoft Excel document, for example, can't be opened with Microsoft Word. To figure out how to open a DAT file with Microsoft Word, you need to do some detective work to figure out which program it's associated with.
Open Microsoft Word. Wait for the program to load completely.
Click "File" and select "Open." Once the Open dialogue box launches, find the DAT file you want, click on it and press "OK."
Examine the file. If this is a DAT file for a Word document, it's easy to read all the data for the particular word document it's associated with. If it looks like a jumble of strange characters, it is associated with another program and you must open it using other methods.
Open a rich text editor like Notepad or TextEdit. Click "File" in the menu bar and select "Open," and choose the DAT file you want to open.
Look at the DAT file. While it will often be a jumble of strange characters, sometimes you can recognise certain elements. For example, you might recognise the names of categories from an Excel document you created months ago. This means the file is an Excel file. If you still can't recognise the file, you will need to use another method to identify it.
Open the document that corresponds to the DAT file. Check that the file looks correct and select "File" from the menu bar. Pick "Save As" or "Export" and find the option that allows you to save the file as a text (TXT) or rich text format (RTF) file. Click the "Save As" or "Export" button when finished.
Launch Microsoft Word. Click "Open" and find the TXT or RTF file you just saved. Select it and press "Open."
Find the DAT file you wish to open. Right-click on the file and select "Open With." This brings up a list of files.
Open the DAT file with each of the programs in the "Open With" menu. This is a tedious process, but when you've found the correct program the DAT file will display correctly.
Save the file as a TXT or RTF file within the program it's associated with. For example, if it turns out the DAT file is a PowerPoint file, click "File" in PowerPoint and choose "Save As."
Open Microsoft Word. Click "Open" and find the RTF or TXT file you saved from the DAT file. Click on the item and press the "Open" button.
When displayed correctly, the DAT file contains information about the specific file it's associated with. It might include information about the vendor or text from the file itself.