True, Mandy. In 2008, the Supreme Court was interpreting this amendment, and Justice Scalia found the right to bear arms to be an individual right "consistent" with the overriding purpose of the 2nd Amendment, to maintain strong state militias. Scalia wrote that it was essential that the operative clause be consistent with the prefatory clause, but that the prefatory clause did not limit the operative clause.
But why have a prefatory clause at all, if not to modify the operative clause? PLus they conveniently ignored the fact that the amendment does not grant individual rights, only the right of the people, as a body, to be secure through the protection of an armed (and well regulated) militia.