Assuming the drive where your videos/downloads/documents are, is NTFS. Run this
sudo apt-get install pysdm
press the windows key in your keyboard. and Type in storage device manager. When prompted give your password. Select your drive2(sda1/2/3) whichever you have your media files on 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 ppa:tualatrix/ppa
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. Select which folders you want to change.