Here's a little snippet of VBA to do that:

   For Each nme In ActiveWorkbook.Names
       nme.Delete
   Next nme

I can't remember who posted it originally, but I find it very useful.

Hope this helps

Pete

Download and install Name Manager (link below).  It is a great tool for
managing all of your named ranges.  In Excel 2007 a similar tool is included
as default, until then gotta do this extra little step:

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