how to set defaultChecked in firefox and IE7

[puniva]

Greetings all,

Please help me to get the solution to get defaultChecked perform well in both firefox and IE7.
Previously i use the code below it worked fine in IE6 and firefox.

var myCheckBox = document.createElement("input");

myCheckBox.setAttribute("id", ("check1"));

myCheckBox.setAttribute("type", "checkBox");

myCheckBox.setAttribute("checked", true);

but its not working after i update my IE6 to IE7.
please help me.

Best Regards,
helpless