Disinterested and uninterested are not synonyms; they are two different words with two different meanings.
To be disinterested is to be impartial, unbiased, and neutral, sort of like the referees are supposed to be in football. (Don’t even get me started about SuperBowl 40.) Being uninterested in something means that you have no interest in it and don’t care to partake in it, for example, The referees in Superbowl 40 were uninterested in performing their roles as disinterested parties.
Sherry
Paul’s book–Literally, the Best Language Book Ever;
Everything Language and Grammar 