Copy from Guide: Enable native NTFS Read/Write in Snow Leopard
Rename the original /sbin/mount_ntfs tool:
sudo mv /sbin/mount_ntfs /sbin/mount_ntfs.orig
Create a script like this:
#!/bin/sh
/sbin/mount_ntfs.orig -o rw "$@“
save the script to /sbin/mount_ntfs
sudo chown root:wheel /sbin/mount_ntfs
sudo chmod 755 /sbin/mount_ntfs
Enjoy R/W access to NTFS volumes...
In case you don't like it
sudo mv /sbin/mount_ntfs.orig /sbin/mount_ntfs
and everything is back to R/O.