"Legacy code" often differs from its suggested alternative by actually working and scaling. - Bjarne Stroustrup http://en.wikipedia.org/wiki/Legacy_system
I've heard the Legacy Systems referred to as if they came from the dark ages.
The incandescent light bulb is a legacy system of sorts. 
It might be old, but its still here, and its still working. Until there's a really good replacement that people can afford, they're not going away. You can bash it all you want, but if you can't replace it, you're just bashing it.
I put this in here, because, I read somewhere that XP was legacy software.