Edit your /etc/fstab to have a "umask" setting. Also, you will need to enable users to mount/umount the disc, something along the lines of:
/dev/hdX /mnt/wherever ntfs users,auto,noexec,owner,umask=333,ro 0 0
Is complete overkill and some of those are redundant upon each other in the options portion, however they do not clash so it will work.
For more info on the options section and an entry in fstab alltogether, see man mount.