lo hice todo desordenado ando a las prisas, checalo y comentas
<?
if (isset($_POST["enviar"])) {
$ide[]=$_POST['id'];
$valor[]=$_POST['activar'];
foreach ($ide as $v) {
foreach ($valor as $v2) {
$sql_update=mysql_query("UPDATE registros SET activo='".$v2."' WHERE id='".$v."'",$con) or die("Problemas en el select:".mysql_error()); }
}
}
}
?>
<div align="center">
<center>
<table border="2" width="48%" height="37" cellspacing="0" cellpadding="0" style="border-collapse: collapse" bordercolor="#800000">
<tr>
<td width="15%" height="19" bgcolor="#FFFF99" align="center" style="border: 2px outset #000080">
<b><font face="Arial Narrow" size="2"> Id:</font></b></td>
<td width="6%" height="19" bgcolor="#FFFF99" align="center" style="border: 2px outset #000080">
<p align="center">
<b><font face="Arial Narrow" size="2">Activo:</font></b></td>
<td width="7%" height="19" bgcolor="#FFFF99" align="center" style="border: 2px outset #000080">
<b><font face="Arial Narrow" size="2">Activar:</font></b></td>
<td width="9%" height="19" bgcolor="#FFFF99" align="center" style="border: 2px outset #000080">
<b><font face="Arial Narrow" size="2">Desactivar:</font></b></td>
</tr>
<?
$i=0;
// Imprimiendo los resultados
while($array = mysql_fetch_array($cad)) {
$x=$i++;
$id=$array['id'];
$activ=$array['activo'];
if ( $activ == "" || $activ == "no" ) {
$activo2 = "No";}
else{
$activo2 = "Sí";}
?>
<form name="f1" method="post" action="<? echo $_SERVER['PHP_SELF'];?>">
<tr>
<td width="15%" height="6" bgcolor="#800000">
<span style="font-size: 3pt"> </span></td>
<td width="6%" height="6" bgcolor="#800000">
<span style="font-size: 3pt"> </span></td>
<td width="7%" height="6" bgcolor="#800000">
<span style="font-size: 3pt"> </span></td>
<td width="9%" height="6" bgcolor="#800000">
<span style="font-size: 3pt"> </span></td>
</tr>
<tr>
<td width="15%" height="27" bgcolor="#FFFFFF" style="border: 2px outset #000080">
<p align="center"><b><font size="2" face="Arial Narrow"><? echo $id ?> </font></b></td>
<td width="6%" height="27" style="border: 2px outset #000080" bgcolor="#FFFFFF">
<p align="center"><b><font size="2" face="Arial Narrow"><? echo $activo2 ?> </font></b></td>
<td width="7%" height="27" bgcolor="#FFFFFF" style="border: 2px outset #000080">
<p align="center"><input type="radio" name="activar" value="si"></td>
<td width="9%" height="27" bgcolor="#FFFFFF" style="border: 2px outset #000080">
<p align="center"><input type="radio" name="activar" value="no"></td>
</tr>
<tr>
<td width="37%" height="37" colspan="4">
</td>
</tr>
<?
}
?>
<input type="text" name="id" value="<? echo $id; ?>" style="display:none" />
<tr><td><input type="submit" value="Enviar" name="enviar" style="font-family: Arial Narrow; font-size: 10pt; font-weight: bold"></form></td></tr>
<?
$con=mysql_close($con);
?>
</table>
</center>
</div>