Default font in AIRHelp's left-hand nav pane?

This may seem like a strange question, but does anyone know the name of the default font that is used in the left-hand navigation pane of the AIRHelp window? I'm talking about the AIRHelp window that you install on the user's PC, not the browser help. Any ideas? I'd like to match it and can't figure out which font it is.

Thanks!

Tim