By default, Mac OS X volumes (partitions / hard drives) that are formatted with the Windows NTFS file structure just read. The NTFS file system driver for OS X is simply not possible to write, in all likelihood a commercial interest here lies behind.
Now it is of course handy that you can exchange files with a Windows user on a NTFS formatted hard disk. There are several commercial products available such as Paragon NTFS for Mac, but it is also free and even better!
First download the latest version of MacFuse and install it. http://code.google.com/p/macfuse/
MacFuse enables file system drivers to the kernel without the need to be added. It is a user side framework in which you can add exotic file formats.
Second install NTFS-3G This is a file system driver that you add to the MacFuse framework. There are two versions to download. The "stable" is the most secure and stable option and the "ublio" is a speed optimized version. It is wise to opt for the "stable" version, the "ublio" can corrupt your NTFS volume when you put a USB hard drive from your Mac without your neatly unmounting it first.
http://macntfs-3g.blogspot.com/
After you have installed NTFS-3G and your Mac has restarted, you can read and write to NTFS volumes. The tool provides an automount feature so no additional action is required. Convenient as that!
As an additional offer NTFS-3G also possible to format NTFS volumes with Disk Utility. An addition, you will also now choose from "Windows NT File System (NTFS-3G).
NTFS volumes to monitor and restore you can use the va ntfsfix tool. For all options of the tool, type: man ntfsfix
