Antreas_4 :
http://imageshack.com/a/img923/3971/iCIcSJ.png
i dont know what do you mean by run as Administrator
Right click on the WinDirStat icon, and select Run as Adminstrator.
However...your issue is simple.
Over 1/2 of your 250GB SSD is taken up with .mkv and .mp4 files. 160GB.
Videos.
Move those off to the 1TB HDD. That will fix your issue.