Alternate for a SHOWMODALDIALOG

Hi all

i am having a small problem.In my page i want to open a xml file on click of
a button in a Modal Dialog.

So whats happening is in the javascript function 

function show()
{
var msAttributes =
"status:no;help:no;bord1er:thin;statusbar:no;scroll:no;dialogWidth:905px;dia
logHeight:573px";
showModalDialog("/pages/LSIsampleForm.xml","",msAttributes);
}

The modal window is getting opened but it remains blank.

Is it that the showModalDialog will only understand html files.If so is
there any alternate way for us to open a model window.

Thanks in advance
raghava