I was motivated to find out what could be known about this, and discovered that it was the customer's "My Account" view (which is only visible to a logged-in customer with at least one order completed) that you were talking about. It *is* possible for any of us to look at our own test customers' accounts since you are not talking about malfunction, just poor layout/fit.

The file that generates this page is /includes/templates/template_default/templates/tpl_account_default.php. This is pretty much all hard-coded tables, and you can change widths and alignments right there.
If you make edits, be sure to save the file to /your_template/templates/tpl_account_default.php so it will be protected from upgrades.