Form layout. Vertical Labels vs Horizontal Labels. Images inside

After reading http://www.lukew.com/ff/entry.asp?1502 and http://www.uxmatters.com/mt/archives/2006/07/label-placement-in-forms.php Placing labels above input fields is preferable, but if you choose to place them to the left of input fields, at least make them right aligned.

I have to design a form for a user to create customers records; I mean, a lot of fields and the user has to do this operation several times a day on his day a day.

First I use horizontal labels, centering the form on the screen enter image description here

Then I decide to use the maximum horizontal size of the screen so I went with this enter image description here

And after reading the articles I tested this enter image description here

After all, I think the 1 is the best and the 3 is the worst, what do you think? Please could you give me any advice about the layout of a form with a lot of controls and will be used by a user-worker several hours everyday.

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