I've just discovered the geometry package, which seems like a nicer way of doing things than manually setting a bunch of lengths, and I'd like to set all my margins to 0.75in. I thought this would be easy enough: just input \usepackage[margin=0.75in]{geometry}. But something seemed a bit off; the text seemed a bit too far to the right. So I changed it to \usepackage[margin=0.75in,centering]{geometry}; still no change, everything was still shifted right. Here is a minimal working example - I've changed the margins to 0in, to emphasize the problem:
\documentclass[11pt]{article}
\usepackage[margin=0in,centering]{geometry}
\pagestyle{empty}
\begin{document}
test \hfill test
\vfill
test \hfill test
\vfill
test \hfill test
\end{document}
produces

Is there another option I need to set to get the text area to align correctly relative to the page?
I'm using TeXnicCenter on Windows 7, and outputting to PDF, if that helps.