Excel 2003 SP2+

I had a 2007 workbook that I copied/renamed to 2008 and retained the 2007
workbook.
Now when I open the 2008 workbook I get a message "This workbook contains
links to other data sources. If you update the links, Excel will attempt to
retrieve the latest data...."
How can I find the links mentioned and remove/update them as necessary?
I have about 12 (monthly) worksheets: Jan/Feb/Mar..../Dec etc.
TIA