4.
Switching back to Clone Mode
Ok, so you've gotten your multiple monitor setup configured and working so you have two seperate desktops, but now you want to go back to one desktop but have it displayed on two monitors.
To do this, first.
If you have an ATI based card, just unclick the Extend Desktop on this monitor option in Display Properties > Settings.
Reboot your pc, but leave the monitor plugged in.
Once back up, your 2nd monitor might come alive with a 'cloned' image of whats on monitor 1. If so, your good to go.
If not, you might need to go into: Display Properties > Settings > Advanced Settings (for primary monitor).
Then go to the Display Tabs and see if the monitor is enabled and in clone mode.
Nvidia cards are similar in this respect.
In clone mode, if you watch a movie, it should show the Movie Fullscreen on the cloned monitor. If not, you will need to go into your Display Properties > Settings > Advanced Settings and check for an option, Full Screen Overlay or perhaps an option in the Clone Mode (ATI cards) or Overlays (Nvidia cards).