Così funziona:

echo "<form NAME=\"F2\" ENCTYPE=\"multipart/form-data\" ACTION=\"notizie_allega.php\" METHOD=\"POST\">";
echo "<input type=\"hidden\" name=\"ID2\" value=\"$ID\">";
echo "<input type=\"FILE\" name=\"nomefile\" style=\"width:0px;border:0px;\">";
//echo "<input type=\"FILE\" name=\"nomefile\">";
echo "<INPUT TYPE=\"SUBMIT\" VALUE=\"Invia\" >";
echo "</form>";

Mentre facendo così no.......

echo "<form NAME=\"F2\" ID=\"F2\" ENCTYPE=\"multipart/form-data\" ACTION=\"notizie_allega.php\" METHOD=\"POST\">
Allega File <input type=\"hidden\" name=\"ID2\" value=\"$ID\">
<input type=\"FILE\" name=\"nomefile\" style=\"width:0px;border:0px;\"
onpropertychange=\"doAllega();\">
</form>";

con

function doAllega() {
document.getElementById("F2").submit();
}

perchè? mi occorre assolutamente fare così................mi punta id sbagliato..........