RE: Alienware Laptop has vertical flickering pixels across the screen
Thank you for the update.
Well, if the external monitor works fine, then the video card is good. Since the distortion is seen while in BIOS as well, I suppose the LCD is going faulty.
You could try reseating the display cable and check or try replacing the LCD ribbon cable and check. If the issue is not resolved, then the display assembly needs to be replaced.
As the system warranty has expired, we could help with a paid service call. You could request for a quote here - http://dell.to/1vnT6CQ
If you wish to replace the parts yourself, then you could get the parts through a 3rd party Dell parts seller - http://bit.ly/24F0aRk
Let us know if you have any other queries.