Windows 7 screen flickers horizontal lines randomly

If you mean the Teredo Tunneling, then yes. I disabled and it now has a black arrow pointing downwards, with a white circle around it.

But I haven't done these two steps yet ;
7. Right click on “6to4 Adapter” and select “Disable”.
8. Right click on the selected network card (Wireless or LAN) that you are working
on and click disable, then re-enable it. This is simply to refresh the card which
can also be done via reboot.

As I don't see the 6to4 Adapter. Should I skip to step 8?

https://www.youtube.com/watch?v=m8UdZ0PZm6Q I did as shown on that video to fix the issue with the Teredo Tunneling and it now has no exclamation mark, neither does any of the stuff shown in device manager. They all seem to work now.

But the issue is still here, and now it seems to flicker even at start up( i rebooted). It did not flicker at start up before.

So far i've tried to change to the screen resolution, and screen hertz is on 60 as there are no other options. I changed the text size to 125%(medium), still it did flicker.

I can't see any marks on the screen itself nor have I dropped the laptop in any recent time, if this information is of any help. Starting to get a bit frustrated.

Other suggestions?

I actually visited that site today via searching on google before I made this thread, and followed the steps. It still did not help.

The only thing I didn't do was the last two steps (check the video card, and the check the monitor) because I don't feel comfortable enough in my IT knowledge.

I don't know what that means, sorry. It's a laptop, with the usual 15.4".

Acer Aspire 5920 Laptop specs This one.