Google 404 and .NET Custom Error Pages

I've got an ASP.NET 2.0 website with a custom 404 page. When content is not found the site serves the custom 404 page with a query string addition of aspxerrorpath=/mauro.aspx. The 404 page itself is served with an HTTP status of 200. To try to resolve this I've added

    protected void Page_Load(object sender, EventArgs e)
    {
        Response.StatusCode = 404;
    }

I added the Google widget and have two issues with it. In Internet Explorer 7 it does not display where it should. If I add it to the content, I get an "unknown error" on char 79 line 226 or thereabouts; if I add it to the head section the search boxes appear above the content. In Firefox it works fine.

So my issues are:

1. How do I make the widget appear inline?
2. How do I make the error page render as a 404 with the original name and path of the file being requested so that when I request mauro.aspx I get the content for the 404 page, but with the URL of mauro.aspx? (I assume that I will have to do some URL rewriting in the begin_request global.asax file, but would like this confirmed before I do anything silly.)

I've handled the 404 by doing this in the global.asax file

protected void Application_BeginRequest(object sender, EventArgs e)
{
    string url = Request.RawUrl;
    if ((url.Contains(".aspx")) && (!System.IO.File.Exists(Server.MapPath(url))))
    {
        Server.Transfer("/Error/FileNotFound.aspx");
    }
}

Now, if anyone can help me with the google widget that would be great!