Alright I know most people know this but for those who somehow don't and annoy the shiz out of people with big images and big white gaps heres how you do it.
Step 1:
You've probably just got a pk or something and uve hit printscreen.
Open up paint: Start>all programs>accessories>Paint
Step 2:
Paste your image into paint (crtl+v)
Step 3:
Now we are gona crop it, located the side and bottom blue markers, or the diagnol one to drag in the sides u wish to crop:
Step 4:
Now just Drag em in till everything is cropped
Ok now if your image wasn't like mine and u need to drop from the left or top of the page you have 2 options
Option 1:
Go Image>flip rotate

Flip by angle 180 degrees
Then apply the previous cropping steps and flip ur image back by 180 degrees
Option 2:
Grab the rectangle tool and seleect the image u want for the end product

once you are satisfied with what u have selected, hit crtl+c (copies it)
open a new document, file>new, then hit crtl+v and it will paste the image u want, if there is any white just bring in the left and bottom margins.
The end, now no more bad crop jobs

If theres anything rong with my guide let me know and i'll make the adjustments and if its the rong forum just move it :p