you have to have ntfs support compiled into your kernel. its quite experimental, however the readonly access is pretty safe.
enabling write support is a separate option, and not recommended.
from the kernel config help:
NTFS is the file system of Microsoft Windows NT. Say Y if you want
to get read access to files on NTFS partitions of your hard drive.
The Linux NTFS driver supports most of the mount options of the VFAT
driver, see Documentation/filesystems/ntfs.txt. Saying Y here
will give you read-only access to NTFS partitions.
and the write support:
If you say Y here, you will (maybe) be able to write to NTFS file
systems as well as read from them. The read-write support in NTFS
is far from being complete and is not well tested. If you say Y
here, back up your NTFS volume first, since it will probably get
damaged. Also, download the Linux-NTFS project distribution from
Sourceforge at <
http://linux-ntfs.sf.net/> and always run the
included ntfsfix utility after writing to an NTFS partition from
Linux to fix some of the damage done by the driver. You should run
ntfsfix _after_ unmounting the partition in Linux but _before_
rebooting into Windows. When Windows next boots, chkdsk will be
run automatically to fix the remaining damage.
Please note that write support is limited to Windows NT4 and
earlier versions.