But as u said it was buddha's aspiration to attain enlightenment and to know the truth of life and not the desire, but the word aspiratoin itself has one meaning as high desire(another is hope to achieve something),also if we consider the latter one then but the question arises that how came the Buddha hope to achieve something in his young age as he even did'nt know thw meaning of enlightenment.He must have desired to know the truth of life.
As I had forewarned in my reply that this discussion might prolong because of "semantic". I also stressed that "desire" in our worldly interpretation involves satisfying the physical senses. What you are referring is not related to satisfying the physical senses, but searching for the ultimate liberation from the cycle of birth and death.
As for the Buddha's quest (I am trying my best to use a neutral word) to know the truth, it was not a one-life decision, but through a very long period of past existence.
I am sorry I think this is the best I can answer you. May I repeat what I wrote:
Have peace, justinchoo :-)