Because this came up last week. Consolas is a ClearType only monospaced font. Ships with Vista, can also be downloaded separately for Visual Studio users.
http://en.wikipedia.org/wiki/Consolas
Consolas Font Pack for Microsoft Visual Studio 2005
And while you’re at it, make sure your ClearType is turned on, and you’ve configured it properly using the ClearType tuner (for XP and Vista).