If the DAT file you're trying to open is text, you can convert the file into text in the Microsoft Excel program by first saving it as a CSV file.

Fortunately, you can convert Excel files to plain text files, which can then be imported into almost any spreadsheet program, such as Intuit's QuickBooks accounting software.

Learn how to import or export data from a Text file to convert a Text (.txt or .csv) file into an Excel (.xlsx) spreadsheet easily using this procedure.

1] Convert Word to plain text, import to Excel, and save in Excel format You can try this simple trick if you want to convert a Word document to Excel without using a third-party tool or application.