Hooking MacBook up to external monitor (please help)

[macness]

Hey guys. So I finally have a desk so I can hook up my late 2011 MacBook Pro to an external monitor. I've tried a couple monitors using mini display port to HDMI. Here's my question: I know that my MacBook is not "hd" but how come when I hook it up to an hd monitor it doesn't display in HD. I hooked up my MacBook to a samsung monitor in best buy yesterday and the pixels were horrible. Why won't it display in HD?