does position () work with old MS namespace

when I added a construction like the following to my XSL, I got an
unspecified error from IE5... is position() one of those things that isn't
supported by the old MS namespace?  Upgrading to MSXML3 isn't an option
right now--is there any other way to treat the first item differently from
the rest?  Thanks.  Eric
    <xsl:choose>
      <xsl:when test="position() = 1">
        <!-- processing for first item -->
      </xsl:when>
      <xsl:otherwise>
        <!-- processing for subsequent -->
      </xsl:otherwise>
    </xsl:choose>


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