Configuring dual screen mode for VGA and HDMI

How can I configure the my dual screen setup to run properly in dual boot mode? When both are connected VGA goes blank at GRUB and GRUB appears on HDMI then after Grub HDMI goes blank and VGA zooms way in so desktop is inoperable. If I disconnect HDMI before boot VGA works properly and then I can connect HDMI which then works properly as well. Please be patient and respond with detailed instructions I am still learning linnux and Ubuntu.