THE PROBLEM: When you hook up your PC to your TV using HDMI, not the whole picture mirrors to the TV, just portions (for me it was the background screen)
The solution: (brace yourselves..)
- Go to System Settings

- Under Hardware, open Displays

- Plug in your HDMI cord (with the tv turned on and ready)
And tick the "Mirror displays" and apply/save changes.

Voila. Simple.
Enjoy your HDMI experience.