My question should be pretty simple.
I have 12.10 with Gnome 3.6 as desktop, and I was wondering if it is possible to shutdown my computer and then start up again and all my windows and screens was restored from earlier, and just popped up again as before?
Hibernating your computer should help.
As Wikipedia page for hibernation says:
To enable hibernation:
gksudo gedit /var/lib/polkit-1/localauthority/50-local.d/hibernate.pkla