what do you mean linked? As in just the title is there, but the actual video file is missing. Or is the actual video file still there and playable?
If the video still plays, and the file is still there, then the video is probably installed on the internal memory.
Now, another thing you can try is using the file manager.
First figure out where you installed the videos, I put my videos in a folder on the internal memory called DCIM, then under videos.
You may try this, just subsitute your folder for DCIM.
example)
go to application>files>DCIM>videos> find the video you want, long press your finger on it, options come up, one option is delete, hit delete.
hope that helped.