Generally this is shown as a link, especially on the web as it's a Secondary Action. LukeW has a good article on the topic: Primary and Secondary Actions in Web Forms.
Link as a control, not a "link" is occasionally contentious, but it's a very clear way to present a secondary, less common action without interrupting the normal workflow or introducing confusing extra buttons.
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The nice thing about the link format is it encourages you to read the text before clicking it. Too often in dialog boxes people just click whichever button looks to be the "default". Here there's only one button, the "default", sign in, so there's little room for confusion.
The Primary Action is usually put at the "end" of the form, hence the bottom right positioning here, typically the place you can find the "confirm"/"okay"/etc. button. But what's really more important is that it is clearly the "submit" button and the other action is clearly secondary; if the link and button were replaced, the button still has significantly more visual weight.