os pongo todo el código a ver si me podeis echar una mano plis ;)
 
<html><head>
<title>Correu amb arxius adjunts</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<body> 
<?php 
   if ($_SERVER['REQUEST_METHOD']=="POST"){ 
// destinatari   
   $to="
[email protected]";
// asumpte del correu
   $subject="Correu amb arxiu adjunt"; 
   $missatge = $_POST['fromname'] ."\n";
   $missatge .= $_POST['fromnick'] ."\n";
   $missatge .= $_POST['fromclan'] ."\n";
   $missatge .= $_POST['fromemail'] ."\n";
   $missatge .= $_POST['comentaris']; 
// aquí agafem el nom i email que s'ha introduit al formulari
   $from = stripslashes($_POST['fromname'])."<".stripslashes($_POST['fromemail']).">"; 
   // generate a random string to be used as the boundary marker
   $mime_boundary="==Multipart_Boundary_x".md5(mt_ran  d())."x";
   // store the file information to variables for easier access
   $tmp_name = $_FILES['filename']['tmp_name'];
   $type = $_FILES['filename']['type'];
   $name = $_FILES['filename']['name'];
   $size = $_FILES['filename']['size']; 
   // here we'll hard code a text messge
   // again, in reality, you'll normally get this from the form submission 
   // per si vols ficar el nom de l'arxiu dins el missatge:
   // $message = "Here is your file: $name\n\n".$missatge;
   $message = $missatge;  
   // if the upload succeded, the file will exist
   if (file_exists($tmp_name)){
      // check to make sure that it is an uploaded file and not a system file
      if(is_uploaded_file($tmp_name)){
         // open the file for a binary read
         $file = fopen($tmp_name,'rb');
         // read the file content into a variable
         $data = fread($file,filesize($tmp_name));
         // close the file
         fclose($file);
         // now we encode it and split it into acceptable length lines
         $data = chunk_split(base64_encode($data));
     } 
      // now we'll build the message headers
      $headers = "From: $from\r\n" .
         "MIME-Version: 1.0\r\n" .
         "Content-Type: multipart/mixed;\r\n" .
         " boundary=\"{$mime_boundary}\"";
      // next, we'll build the message body
      // note that we insert two dashes in front of the
      // MIME boundary when we use it
      $message = "This is a multi-part message in MIME format.\n\n" .
         "--{$mime_boundary}\n" .
         "Content-Type: text/plain; charset=\"iso-8859-1\"\n" .
         "Content-Transfer-Encoding: 7bit\n\n" .
         $message . "\n\n"; 
      // now we'll insert a boundary to indicate we're starting the attachment
      // we have to specify the content type, file name, and disposition as
      // an attachment, then add the file content and set another boundary to
      // indicate that the end of the file has been reached
      $message .= "--{$mime_boundary}\n" .
         "Content-Type: {$type};\n" .
         " name=\"{$name}\"\n" .
         //"Content-Disposition: attachment;\n" .
         //" filename=\"{$fileatt_name}\"\n" .
         "Content-Transfer-Encoding: base64\n\n" .
         $data . "\n\n" .
         "--{$mime_boundary}--\n"; 
      // now we just send the message
      if (@mail($to, $subject, $message, $headers)){
	  	  if (@mail ($fromemail, "Inscripció Torres Lan Party","La teva inscripció s'ha realitzat correctament.")){
         echo "<tt>Missatge enviat.</tt>";
		 }
		 else
         echo "<tt>Error en l'enviament del missatge.</tt>";
   } }
} else {
?>
<tt><p>Enviar un correu amb arxiu adjunt:</p>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" enctype="multipart/form-data" name="form1"> 
<br>Nom ................. <input type="text" name="fromname">
<br>Nick ................ <input type="text" name="fromnick">
<br>Clan ................ <input type="text" name="fromclan">
<br>Correu electrònic ... <input type="text" name="fromemail">
<br>Arxiu ............... <input type="file" name="filename">
<br>Comentaris:<br>
<textarea name="comentaris" cols="35" rows="5"></textarea><br>
<input type="submit" name="Submit" value="Enviar">
</form></tt>
<?php } ?>
</body>
</html>