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.

Luckily, Excel offers handy formulas that allow you to convert text into upper case, lower case, title case, and even sentence case with minimal effort.

Microsoft Excel has an import wizard, but if you structure the text correctly, you can bypass the wizard altogether.

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.

Edmond Woychowsky walks you through his process, including all the necessary sample code, to convert an XML file to an Excel spreadsheet.