How can I write a hard drive sector as reserved?

I am hex editing a hard disk and I would like to mark some hard drive sectors as reserved so that they are not overwritten by Windows (Vista or 7). I think this is possible, since during a defrag, the disk says that t开发者_StackOverflowhere are some sectors that aren't movable.

How can I do this?

---

Have you considered marking them as bad blocks within NTFS? This will make Windows bypass them completely.