Earlier versions of Word did not count footnotes in the word count. Word 2010 does (although there may be an option for this).

The word count in Windows properties is usually different from that in Word and the one in Word is accurate AFAIK. For very short documents (single page, no headers, footers, footnotes, etc.) they will be the same.

When an attorney files a brief in the appellate courts in Wisconsin, that attorney must personally attest to the number of words in the brief (or at least that it does not exceed a certain maximum), so this is something I keep track of.