I don't know for sure, but at the moment Word is probably getting its data
using an obsolescent method (DDE) from an Excel format (.xls) that should
also be considered obsolescent now that you are using Office 2007.

In your situation, I would probably
a. make sure I had a backup copy of my Word 2000 and Excel 2000 documents
b. open my Excel 2000 document in Excel 2007 and save it in the native
Excel 2007 format.
c. open my Word 2000 document and try to connect to that new Excel 2007
document. If successful, save the Word document in Word 2007 format (.docx,
or .docm if it contains macros)

However,  when you use DDE, Word tends to display the data more or less as
you saw it in Excel. Once you have done (c), the chances are that you will
no longer be using DDE and all your field results will look different. At
that point I suggest you have a look at http://tips.pjmsn.me.uk/t0003.htm -
it doesn't cover Office 2007, and in particular, how to change the way Word
2007 connects to Excel  2007, but I believe most of the material is still
relevant.

Peter Jamieson