Here is an example of a line you've to add/change at /etc/fstab
/dev/hda1 /mnt/win_c vfat uid=500,gid=500,umask=000,exec,dev,suid,rw 1 0
Assumming that you have a directory called /mnt/win_c and that hda1 is your windows partition. Just change the numbers to fit your needs better.
Remember that you cannot write to NTFS yet. It's safe to do it with FAT32 windows partitions.