This style is made by request. It is a combination of Harvard referencing with numbers.
Copy the style to your Word 2007 style directory, open Word 2007 and select 'Chicago Numbered Extension' from the reference tab.
Due to the limitations of the Word 2007 bibliography numbering system, the bibliography entries are not ordered alphabetically but rather by their occurence as in-text citations. If you want to keep them alphabetically (and get the numbers all mingled up), you just have to comment out (or remove) line 3971 from the stylesheet:
<xsl:sort select="./b:RefOrder" data-type="number"/>
The latter can be useful if you plan on editing the numbers by hand afterwards.