conviene preparare una funzioncina
codice:
<script type="text/javascript">
function abilita_disabilita(rd){
 var bool=(rd.value=='si')?false:true
 with(document.forms['nomeform']){
  nomeselect.disabled=bool
  nometext1.disabled=bool
  nometext2.disabled=bool
 }
}
</script>
<form name="nomeform">
<input type="radio" name="nomecheck" value="si" onclick="abilita_disabilita(this)" />sì

<input type="radio" name="nomecheck" value="no" onclick="abilita_disabilita(this)" />no

<select name="nomeselect" disabled="disabled">
<option></option>
</select>

<input type="text" name="nometext1" disabled="disabled" />
<input type="text" name="nometext2" disabled="disabled" />
</form>