I have a dell 1520 inspiron.. and just now i found on the mid top of the screen a white horizontal line running from right to left side, facing the laptop.. i just want to ask what's the probable cause of that even if its not dropped or broked.

You could try removing the display device in device manager then rebooting. At boot up windows will reinstall the drivers.
Check for new display drivers at Dell's support site.

Right click your mouse on your desktop and a box will pop up. Select the bottom line, which should say Settings for XP, or Personalize for Vista, Windows 7 or 8 and left click on it. Another box will appear which will have top tabs. Select the second one in for screen saver. In the left center it will show the current screen saver, which is where you can select another or none. Below that is a box for setting the time for when the screen saver will start. Let me know how you do. or what you may need.

If the white line is in the middle of the screen and runs left to right the problem is in the vertical circuit of the set.

Either a bad part in that area or at the vertical output chip bad solder connections (most with this will react when set banged on side).

Note: leaving set on with only that line on screen will sooner or later burn that mark into the face of the screen--not fixable.

Gciappa,

Dell Support > Inspiron 1520 Notebook PC > Service Manual,

http://support.dell.com/support/edocs/systems/ins1520/en/sm/index.htm

Click on Coin-Cell Battery in the right hand list.

1) Remove ALL power. Remove the AC adapter (Charger), and Battery.

2) Suggest lay a soft static free cloth on the table you're working on. Helps prevent scratching the table, and laptop.
Turn the laptop over, Battery Compartment facing away from you.

3) Remove the Memory Compartment Cover,

http://support.dell.com/support/edocs/systems/ins1520/en/om_en/html/about.htm#wp1175774

(Number 2 - memory module/coin-cell battery compartment )

The RTC Battery is that small plastic 'bag', that has a Red and White wire coming out of it, and ending in a small white plug connector.

(Real Time Clock Battery. Term coined now for CMOS Battery )

Replace battery, close cover, reinstall main battery, and AC adapter.

Regards,
joecoolvette

I think you are on the right track for a connection problem. As the computer heats up things expand and the connection would become tighter. The tapping is another key that this is possible.

if it works fine in safe mode you should try a system restore . most of the time a problem that gos away in safe mode is driver related . IE software don't think you have a hard ware issue. you can call dell if you do not have the disk . 1-866-751-6079 call this number it's dell's Spanish tech support number but this is the fastest way to reach a real person at dell . just ask them to speak English and they will.

As it works ok in safe mode, I suggest you check that your graphics drivers are up to date.

You should be able to download the latest from the Dell website.

You got a bad LCD screen. no immediate resolution aside from getting the LCD replaced. if your system still has warranty call Dell for replacement.

Hope it helps!

make sure there are no speakers at the side of the monitor as the may not be sheilded. then unplug monitor from the mains and plug back in to reset. or in the monitor menu select degauze .

Screen cracked, you will need to order a new screen and replace it.

Here is how to replace screen on Dell Inspiron E1505.