The Personal.xls workbook has historically been used to store macros and customizations that you want shared among all the workbooks on the system. Barbara updated to Office 2007, but her company has dictated that files created in Excel 2007 be saved in Excel 2003 format since many of their clients have not yet upgraded. Barbara is wondering if she should continue to use Personal.xls as the personal macro workbook or copy all macros to Personal.xlsb.
Honestly, you can’t make that choice in Excel 2007. If you are using the program, all of your macros that previously were stored in Personal.xls should be transferred to your new Personal.xlsb file. Why? Because the Personal.xlsb file is for use on your machine, so there is no issue of backward compatibility for your clients. Workbooks that you save in the older Excel 2003 format will continue to save just fine and be readable by your clients using the older version of Excel.
If, however, you have clients with whom you need to share the macros in your Personal.xlsb file, and they aren’t using Excel 2007, then you will need to unhide the workbook and save it in the older format explicitly. It is this older format that you will save with them, and such saving will still not affect the Personal.xlsb file on your system.