Before and Afters In CS5

Working on my Adobe Photoshop Cs5 skills in Digital Photography class. Here's a shot I was messing with various selection tools and curves to improve.

Before:

After: (*changed the light bulb, the globe, the sky, and trim and shadows on the house.)

Photography Class-Story of My Life.

I hate Macs. And I am not all that experience in Photoshop CS5. This is the story of my life right now...

COMMAND Z COMMAND Z COMMAND Z. 
*I hit CTRL Z over and over again and get mad that it isn't undoing. Yeah. Im a PC.