Hi @kintaro87, following steps might help! 1. Right-click the old excel file, and under Properties change the 'Opens With' option to Excel. 2. Since this is an old excel file (.xls), chances are it might be under 'Protected View', not allowing you to edit. If so, go to File -> Info -> Select File Block settings under Protected View. This will open the Excel Trust Center. 3. Apply checkmarks as required and save the file. This will remove the protected view. 4. If you were able to edit the file (no Protected View highlight), then simply Save As the file as a newer version of Excel. 5. Using OneDrive, you can sync your excel file to Office 365 and open the file in Excel 365.