Why won't the screenshot tool take Full 1920x1080?

[mattixface]

I run a few games near perfectly in Full 1080p HD on my computer... Smash Bros Brawl is one of them... but when I hit F9 or whatever it takes a screenshot sometimes at 1700 something by something else... and other times at 1600something by something else... why won't it take a full shot? ... no one believes me that it's runnig in full HD and I can't prove it with screenshots!... haha!... it would be nice...