Using a page compiled into an assembly

I am developing a ASP.NET SpellCheck control. For this I also have a
simple html/aspx (popup.html) page which will be opened when user
clicks on a button to check spelling.
In the control i inject script for opening the popup.html using
window.open() but ASP.NET cant find the page obviously because the
page is in the control library and not in the website root directory.
I dont want to force the user to copy the popup.html to his website
root directory before he can use the spellcheck control. So how can i
achieve that?