For example, when you search for [intel solid state drive toolbox], Google's list includes two strange suggestions: [intel solid state drive toolbox(intel ssd toolbox)] and [intel® solid-state drive toolbox download]. It's really unlikely that many people search for [intel®] or include redundant versions of the query.
The real explanation is that a lot of pages include those texts and Google used them to enhance Google Instant.
What about the standard navigation links used by Google or Bing? Obviously, they're included in a lot of pages and few Google users would search for boilerplate text and also use special characters.
Google's help center page for autocomplete informs users that "Google's algorithm predicts and displays search queries based on other users' search activities and the contents of web pages indexed by Google".