[CentOS] problem mounting external drive

On my Centos box with:
  uname -r
  2.6.18-164.6.1.el5

I tried to mount my 2T external drive with:
   mount -t ntfs /dev/sdg1 /mnt/wd

and I get:
   mount: unknown filesystem type 'ntfs'

Thanks in advance for your help.
Mike.