help needed in saving Excel 2003 workbook modified and to be saved in Excel 2007

[great-scot]

I'm new to Excel. I use Excel 2007 on a Win XP machine. Forgive me if my question/ explanation seems confusing but, to be fair, I'm confused myself.

I'm using Excel 2007 to open an Excel 2003 workbook (therefore I'm running in compatibility mode).

I'm able to open the workbook, add or modify data and save the workbook -however I can ONLY save the workbook by using the original file name and over-writing the original file.

I've tried to use the "save as" command to give the workbook a different name but nothing happens. I've even tried to create a new workbook and copy sheets from the Excel 2003 workbook into it and save it with a different name but the file won't save unless I use the original file name.

I'm not sure what I'm doing wrong. Any solutions?

Thanks in advance for your help.