Well you left the rest of the screen, just colored everything else white.
Here's what you can do...
Cap the screen you want.
Open Paint.
Click Edit > Paste
then use the cropping tool (circled in red)
And crop out the image you want.
Too explain it easier..
then, with the part of the cap you want cropped with the tool, just click Edit > Copy.
then open a new paint, hit edit paste, and then you can have the image alone.