I'm not sure about other colleges, but the college I attended has a drop date from the time of registration to sometime after the start of the class. Check with an advisor and they can help you out.
I have been accepted into college (assuming I get the right grades) and I should start in September, but I'm not sure about the subjects I've chosen. Is it too late to change/drop any of them?
Try to contact your schools dean of administration and ask them. They'll be able to give you the best answer. But from my own experiences (although it's from high school and not college) I've changed my courses around during the school year. I would assume it's not too late. Good luck!