FYI, when I open C:\Windows\Fonts in Explorer I see Arial. When I double click it, I get a Font family details screen:

Right-click > Properties on the Arial Narrow font in the above window yields:
What I don't know is whether an app that I have installed brought the ARIALN.TTF file along with it. I don't have a fresh, out-of-the box Windows 7 system to look at right now.
-Noel