When you attempt to import information from a Microsoft Office Excel 2007 worksheet, Microsoft Office Outlook 2007 fails to recognize the file.
By default, Office Excel 2007 uses a new file format that has file extensions of .xlsx, .xlsm, or .xlsb. Office Outlook 2007 does not support opening files in these file formats.
Office Outlook 2007 supports the previous Excel file format, which uses the file extension .xls. You can save your Office Excel 2007 worksheet in the file format used by previous releases of Excel and then import data from that file into Outlook.
Save an Excel workbook in the Excel 97-2003 Workbook (*.xls) format
Important: If you save a workbook in a file format other than a Microsoft Office Excel 2007 file format, formatting and features unique to Excel 2007 will not be retained. For more information, see Formatting and features that are not transferred in Excel file format conversions.
Open the workbook that you want to import into Office Outlook 2007.
Click the Microsoft Office Button , and then point to the arrow next to Save As.
In the File name box, type a new name for the workbook.
Tip: You can also accept the suggested name.
In the Save as type list, click Excel 97-2003 Workbook (*.xls).