Assuming the drive where your videos/downloads/documents is NTFS. run this
sudo apt-get install pysdm
press the windows key in your keyboard. and typ in storage device manager.
when prompted give your password. select your drive2(sda1/2/3) which you have your media files.
select "assistant" select "mount file-system in read-only mode" ok.
and then apply. on the lower left corner hit refresh. now reboot your system.
To change the default folder you must install Ubuntu-tweak like so.
sudo add-apt-repository -y ppa:tualatrix/ppaBeheerders
sudo apt-get update
sudo apt-get install ubuntu-tweak
open ubuntu-tweak via dash
then go to administrators > default Folder locations >
select which folder you want to change. like the folder Documents then
on the lower right screen click edit. and then select to which folder you
want to change to. example /media/sda3/Documents