Gestion des données

salut ,
j'ai un probléme avec l'ajout des données dan ma base a travers d'un formulaire html ;

le code html "ajout.html" :

<form method=post action="test2.php">
<div align="right"><img src="clip_image002.gif" width="60" height="49"></div>

<table width="519" height="227" border="0" align="center" cellpadding="0" cellspacing="7" background="../../../wamp/www/tet/img/back2.png">
<tr>
<td width="221" height="51"><div align="right">Identifiant: </div></td>
<td width="277"><div align="left">


<div align="left">
<input type="text" name="idstation">
</div>

</div> </td>
</tr>
<tr>
<td><div align="right">Utilisateur: </div></td>
<td>
<div align="left">
<input type="text" name="user">
</div>
</td>
</tr>
<tr>
<td><div align="right">@MAC : </div></td>
<td>

<div align="left">
<input type="text" name="mac">
</div>
</td>
</tr>
<tr>
<td><p align="right">@IP :</p> </td>
<td>

<div align="left">
<input type="text" name="ip">
</div>
</td>
</tr>

</table>
<p align="center"> </p>
<table width="200" border="0" align="center">
<tr>
<td>
<div align="center">
<input type="submit" name="Submit" value="Ajouter">
</div>
</td>
<td>
<div align="center">
<input type="reset" name="Submit2" value="Annuler">
</div>
</form></td>

et le code php "test4.php :

<?php
$db = mysql_connect("localhost", "root", "");
mysql_select_db('pc',$db);
if ( isset($_POST) && (!empty($_POST['user']))) {
extract($_POST);
$id2 = $_POST['id_station2'];
$sql = "DELETE FROM pc WHERE pc.id='".$id2."' LIMIT 1";

mysql_query("$sql") or die('Erreur SQL : <br />'.$sql);

mysql_close();
}

?>


et le code d'erreur : Erreur SQL :
INSERT INTO pc VALUES("123", "lrjlk", "lkfjl", "lkjfl",")