okay just bare with me it sounds weird but...
okay in halo 2 the UNSC and ONI had a secret mission to make cortana a human they did and they call her DARE so know one would know that she was cortana but she was test one so they was problems, but the UNCS and ONI didnt see, they put her in a squad made up of The Rookie, Dutch, Romeo, Buck and Mickey.
okay from here on in ive got two different theorys.
Theory ONE : DARE betrays her fellow sqaud (KILL THEM) The UNSC and ONI found out and order The Rookie to kill her.
Theory TWO : The Superintendent (like runs the garbage trucks and the phone line and the signs) founds out and somehow kills her.
then it goes on to halo 3 and instead of trying again they use cortana in hologram form.
That is just my theory on DARE.
Its a THEORY PEOPLE im not saying that is what happened
Thanks for reading,
-Dredfire :P
[Edited on 06.06.2009 10:59 PM PDT]