So I was at my sister's place, getting my hair dyed and giving her some music and a movie from a laptop drive that I put in that external enclosure I got from the last winter FITES event.

She wanted to give me a cam rip of a recent movie but couldn't write to the drive. I could, obviously, because I put the music and movie on it. Only difference is that I use Win8 and she's using a mac.

Why is this? Write protection or something? The properties for the drive as displayed in OSX (or 10.x or whatever it is now) said it couldn't be written to or it was read only or something.

Yes, IIRC Mac can read NTFS but not write. (At least without a different NTFS driver.)

http://www.macbreaker.com/2012/02/enable-write-for-ntfs-hard-drives-on.html