This is a custom style based on the IEEE style v.2.4. Instead of reference order numbers, tags are used to identify citations.
Copy the style to your Word 2007 style directory, open Word 2007 and select 'IEEE with tags' from the reference tab.
Using tags over numbers gives you the capability to sort the entries in the bibliography in whatever order you want. For example, if you wanted to sort the references in the bibliography based on the tag rather than their occurence in the list, you would change line 198 from:
<xsl:sort select="b:RefOrder" data-type="number"/>
<xsl:sort select="b:Tag" data-type="text"/>
Remember, if you want to sort the entries based on the authors name, it is not always as easy. You have to take special care for cases where there are no authors, or where the authors are actually the editors for example.