It could be more specific if you'd extend that ie:
PHP Code:
$been_here = mysql_query("SELECT id FROM statistical WHERE ip = \"$_SERVER['REMOTE_ADDR']\" AND os = \"$_SERVER['HTTP_USER_AGENT']\"");
But then again, in these M$ days, this wouldn't catch that many if they were sharing IP.
And if the viewer were to have multiple boot options, this would srew it up aswell.