<input type="radio" name="radio1" onclick="document.all.text1.disabled=false;document.all.text2.disabled=true" checked>
<input name="text1" type="text">
<input type="radio" name="radio1" onclick="document.all.text2.disabled=false;document.all.text1.disabled=true">
<input name="text2" type="text" disabled>
<input name="text1" type="text">
<input type="radio" name="radio1" onclick="document.all.text2.disabled=false;document.all.text1.disabled=true">
<input name="text2" type="text" disabled>
<input type="radio" name="test" value="rB" onclick="document.all.tA.disabled=true;document.all.tB.disabled=false"><input name="tB" disabled>