is there a dark mode skin for Windows Live Messenger 2009 or Older?
Nope, but you could try this skin:
Download link: Phunkn---Infusco-2.0.4.plsk - Google Drive
Thank you! Is it for 2009 or older?
as you can see in the screenshot on the embed, its for 8.5.
I use it on WLM 2009