When you click your mouse on one of the input fields in a form, you will get the onscreen keyboard on Windows Phone 7 emulator. It’s worse than using your thumbs on your real phone because you actually has to click one character at a time with your mouse.
Now, while you still can see the onscreen keyboard, press the [Pause/Break] key (to the right of [Scroll Lock] key, at least on my keyboard–my computer keyboard). If you do it right, the onscreen will disappear and you can do your form entry with your physical, full-size keyboard.