Well. You need to mention what distro you are running for starters. A good way to find out in terminal is
$ cat /etc/issue
Welcome to antiX. Powered by Debian Testing and MEPIS.
$ lsb_release -a
Distributor ID: Debian
Description: Debian GNU/Linux testing (wheezy)
Which Desktop you are running like KDE,Gnome 2,Unity,Gnome 3, Icewm, XFCE, E17, Fluxbox, I think I covered newbie desktops.
That would be a good starting point for your next post. Also state exactly what you did to create the problems. Think about what exact steps you took to use dual screens in next post and I am sure members will help if you elaborate better and give more detailed info. We are not mind readers here or standing behind you looking over your shoulder. We are flying blind in this thread so far.
Happy Trails, Rok