[Kyle76]

How do I set the permissions on an external NTFS hard drive so that I can write to it? It now says read only. I have been using it on a Windows XP computer, but would like to be able to use it on my MBP as well.

[olePigeon]

NTFS is a proprietary file system from Microsoft, they don't want other people reading/writing to it. So naturally, people got together and reverse engineered it in spite of Microsoft. What you need is MacFUSE, and NTFS-3G.

NTFS-3G is a file system plugin for MacFUSE. This will allow your Mac OS X system to read & write to NTFS partitions. It is exceptionally handy when dual booting your MacBook Pro with Windows.

While you're at it, you should pick up MacFusion. It's a graphical utility for MacFUSE which allows you to mount FTP/SFTP right to your desktop as if it were a network disk. It's really awesome if you use S/FTP a lot, or SSH to upload/download files.

[mduell]

No amount of permissions changing will allow OS X to natively write to NTFS. You need install third party software (MacFUSE and NTFS-3G, Google them) to enable writing to NTFS (albeit slowly).

edit: olePigeon beat me to it, and with links!