You must be trying to access your NTFS partition as a regular user, without administrative priviledges.
What happens when use the "Disks" application is you get asked for your password so that you do get those priviledges...
You can do the same by invoking nautilus from a command-line as such: and then browse to your Windows folder.
Another way around it is to give access to your NTFS to all users, by adding the option "umask=0002" to your ntfs line in /etc/fstab. My /etc/fstab looks like this:
This way, you can just go to that partition without priviledges, using no-matter what program, without being asked a thing...
# /etc/fstab: static file system information.
# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
/dev/hda5 / ext3 defaults,errors=remount-ro 0 1
# /dev/hda1 /windows ntfs defaults 0 0
/dev/hdc /media/cdrom0 udf,iso9660 user,noauto 0 0
/dev/hdd /media/cdrom1 udf,iso9660 user,noauto 0 0
/dev/fd0 /media/floppy0 auto rw,user,noauto 0 0
/dev/hda1 /windows ntfs-fuse auto,gid=1001,umask=0002 0 0