Take out the javascript onclick and make it an "HREF=" then within the a tag set the target='_new' and it will open as a new window.
<a HREF="EditMetric.aspx?sid=" & myDataTable.Rows(0)(1) & "&kpName=" & myDataTable.Rows(0)(0) & """, """", ""fullscreen=yes scrollbars=yes"");' " _
& "style='text-decoration:underline;cursor:hand;' target='_new'>