Underscore and hyphen changed to ASCII code in URL?

Tech-Archive recommends: Fix windows errors by optimizing your registry

From: Daniel A (DanielA_at_discussions.microsoft.com)
Date: 12/07/04 

Date: Tue, 7 Dec 2004 06:45:04 -0800

Hi all,

Why undercores and hyphens in directory names are changed to the ASCII code
by IIS in the URL response? But as long I have a "/" after the last directory
the URL is returned correctly. Exemple this http://website/abc-xyz is
returned like this http://website/abc%2Dxyz. But it is returned unchanged in
those scenarios : http://website/abc-xyz/ or http://website/abc-xyz/index.aspx

Is anyone has an idea why,

Thanks, 

-- 
Daniel