Upload script werkt niet

<?php
if (isset($_POST['knop'])) {
    $sDir = '../tracks/' .$HTTP_POST_FILES['track']['name'];
    if (move_uploaded_file($HTTP_POST_FILES['track']['tmp_name'], $sDir)) echo 'Ja<br />';
    else echo 'Nee<br />';
    @chmod($HTTP_POST_FILES['track']['name'], 0777);
    $sQuery = '
    INSERT INTO
        tracks
        (
        artiest_id,
        naam,
        link
        )
    VALUES
        (
        "' . $_POST['artiest'] . '",
        "' . $_POST['naam'] . '",
        "' . $HTTP_POST_FILES['track']['name'] . '"
        )
    ';
    $iResult = mysql_query($sQuery) or die(mysql_error());
    echo 'Track toegevoegd.<br /><br />';
}
$sQuery1 = 'SELECT * FROM leden WHERE soort = "artiest" ORDER BY artiestennaam ASC';
$iResult1 = mysql_query($sQuery1);

echo '<form enctype="multipart/form-data" method="post" action="">';
echo '<table>';
echo '<tr><td>Artiest:</td><td><select name="artiest">';
while ( $aObject1 = mysql_fetch_object($iResult1) ) {
    echo '<option value="' . $aObject1->id . '">' . $aObject1->artiestennaam . '</option>';
}
echo '</select></td></tr>';
echo '<tr><td>Naam:</td><td><input type="text" name="naam" size="40" /></td></tr>';
echo '<tr><td>Track:</td><td><input type="file" name="track" size="40" /></td></tr>';
echo '<tr><td></td><td><input type="submit" name="knop" value="Voeg toe" /></td></tr>';
echo '</table>';
echo '</form>';
?>