ho fatto così:

<form name="registrazione" action="<?php echo $nome_pagina;?>" method="post" >
<select name="nazione">
<option value="AL">Albania</option>
<option value="DZ">Algeria</option>
<option value="SA">Arabia Saudita</option>
<option value="AU">Australia</option>
<option value="AR">Argentina</option>
<option value="AT">Austria</option>
<option value="BE">Belgio</option>
<option value="BA">Bosnia e Herzegovina</option>
<option value="BR">Brasile</option>
<option value="BG">Bulgaria</option>
<option value="CA">Canada</option>
<option value="CZ">Rep. Ceca</option>
<option value="CL">Cile</option>
<option value="CN">Cina</option>
<option value="CY">Cipro</option>
<option value="CO">Colombia</option>
<option value="CR">Costa Rica</option>
<option value="HR">Croazia</option>
<option value="CU">Cuba</option>
<option value="DK">Danimarca</option>
<option value="EG">Egitto</option>
<option value="FI">Finlandia</option>
<option value="FR">Francia</option>
<option value="DE">Germania</option>
<option value="GR">Grecia</option>
<option value="HK">Hong Kong</option>
<option value="IS">Islanda</option>
<option value="IN">India</option>
<option value="ID">Indonesia</option>
<option value="GB">Inghilterra</option>
<option value="IR">Iran, Rep. Islamica di</option>
<option value="IQ">Iraq</option>
<option value="IE">Irlanda</option>
<option value="IL">Israele</option>
<option value="IT">Italia</option>
<option value="JM">Jamaica</option>
<option value="YU">Jugoslavia</option>
<option value="KP">Korea, Rep. Democratica</option>
<option value="KR">Korea, Rep. di</option>
<option value="JP">Giappone</option>
<option value="LI">Liechtenstein</option>
<option value="LU">Lussemburgo</option>
<option value="MK">Macedonia, ex Jugoslavia</option>
<option value="MT">Malta</option>
<option value="MX">Messico</option>
<option value="MC">Monaco</option>
<option value="MA">Morocco</option>
<option value="NO">Norvegia</option>
<option value="NZ">Nuova Zelanda</option>
<option value="NL">Olanda</option>
<option value="PK">Pakistan</option>
<option value="PY">Paraguay</option>
<option value="PL">Polonia</option>
<option value="PT">Portogallo</option>
<option value="RO">Romania</option>
<option value="RU">Federazione Russa</option>
<option value="SM">San Marino</option>
<option value="SG">Singapore</option>
<option value="SY">Siria, Rep. Arabica</option>
<option value="SK">Slovacchia</option>
<option value="SI">Slovenia</option>
<option value="SO">Somalia</option>
<option value="ES">Spagna</option>
<option value="LK">Sri Lanka</option>
<option value="US">Stati Uniti d'America</option>
<option value="ZA">Sud Africa</option>
<option value="SE">Svezia</option>
<option value="CH">Svizzera</option>
<option value="TH">Tailandia</option>
<option value="TW">Taiwan, Provincia della Cina</option>
<option value="TN">Tunisia</option>
<option value="TR">Turchia</option>
<option value="HU">Ungheria</option>
<option value="UY">Uruguay</option>
</select>
<script>
var str="<?php echo $HTTP_POST_VARS['nazione'];?>";
var sel="document.registrazione.nazione";
for(var i=0; i<sel.lenght;i++){
if(sel[i].value==str){
sel.selectedindex=i;
break;
}
}
</script>
</form>
ma niente da fare; aiutoooooo