Okay Heres a long story short. Today in school the biggest drug user decided that he wanted to give me a hi five, and I gave it to him. I was fine until I realized that I had an open cut on the hand that I touched his with. If he had an open cut on his hand that touched mine, would I be at high risk to develop HIV form him?

This is the question of a "hypothetical risk" vs an "actual risk". In order for that to happen either of you would have to be HIV+ and, I suspect that your reasoning is that, since "he is the biggest drug user in school", he must be injecting drugs (because you certainly can't contract HIV by snorting coke), he has the greater likelihood of being HIV+. And that in order for his cut to come in contact with your cut they would have to be in the exact, but opposite, areas on your high-fivin' hands and both would have to be bleeding. Sure, if that happened then I suspect it is possible for the virus to be transmitted. But, of course, all of those elements would have to fall into place thus making it a "hypothetical risk".