This is a continuation of Orliaurelijah's article on the logos of the past and how they've changed over the years. I'm covering some of the logos he left out.
Xerox
Old

Such a simple, yet iconic logo. Why in the world did they have to change it into this...?
New
Baskin Robbins
Old

The pink and blue colors clash nicely, and the 31 has a nice classic look.
New

That "BR/31" combo looks pretty neat, but I'm not too fond of this logo overall.
NBC
Old (1956-1961)

The original NBC peacock, which was used to represent color TV broadcasts.
(1979-1986)

This is my favorite of all the NBC logos used. It is a simplified version of the 11-feathered peacock combined with the futuristic N used between 75-79. They went with this after a lawsuit from the Nebraska ETV network due to the similarity in the logos.
New (1986- )

An even more simplified version of the previous peacock with just six feathers representing NBC's six divisions. The peacock now looks to the right rather than the left.