1. Double click to open your Microsoft Excel 2010 file.
2. Click the 'File' tab in the upper-left corner, then select 'Save As.'
3. Click the drop-down menu to the right of 'Save As Type' and select 'CSV (Comma Delimited).'
4. Click the 'Save' button, click 'OK' to save the active sheet, then click 'Yes' to keep the worksheet in CSV format.
5. Right click the CSV file you just created, click 'Open With' and select 'Notepad.'
6. Click 'File' at the top of the window, then click 'Save As.'
7. Click the drop-down menu to the right of 'Save As Type' and choose 'All Files.'
8. Click inside the 'File Name' field and add '.dat' to the end. For example, if your filename is 'xxxxxx,' modify it so it reads, 'xxxxxx.dat.'
9. Click the 'Save' button.