You have to edit the file /etc/fstab. Here is an example:
/dev/hda1 /mnt/win_c vfat uid=500,gid=500,umask=000,exec,dev,suid,rw 1 0
That mounts your first partition (/dev/hda1), otherwise, change it for your correct partition, at the folder /mnt/win_c. That, indeed, assumes that you have already created a directory called win_c at mnt (or create now, as root, type: mkdir /mnt/win_c).
After editing that file, you may need to umount and remount the partition or restart your computer. It's your call