Compaq Presario C300. After a few hours of use coloured horizontal lines start to appear then flicker down the screen. If I close it and leave it a few hours it's fine again.

It sounds that one or two of its back-light CCFL lamp/s has burned out. Check it.

This is usually a sign of either a bad LCD screen cable, a bad LCD screen, or a bad display adapter.
If you connect an external monitor & you get a picture without these red horizontal lines, then your display adapter is OK.
Diagnosing a bad LCD screen cable or a bad LCD screen requires that you disassemble the LCD screen panel, & swap them one at a time with a matching part. This way you can identify which part is causing the problem & replace it.

I Think BIOS Problem Download New Bios From Following Link http://h10025.www1.hp.com/ewfrf/wc/softwareCategory?lc=en&dlc=en&cc=us&softwareitem=ob-91811-1&os=4062&product=4308201&sw_lang=&#N468

Using Power Adaptor & With Battery In Laptop Bios Update.

Caution: Plz. Carefully Install BioS.Inpropery Install BIos Laptop is Damage

Hello, It sounds like you have a bad display screen. Here is the replacement.

Hello,

Since the laptop works fine with an attached monitor, it means the problem is the inverter.

The problem with your laptop screen is that the inverter is malfunctioning, that is why you have those three equal horizontal sections.

Change the inverter of your laptop screen and you will see that the screen will be stable back.

Take care.

Try reseating the LCD cable to the video card. If no change, then you will most likely need a replacement LCD (Roughly $150 on EBay)

Hi there.
It sounds like you may have a loose inverter cable or the ribbon cable behind the screen is loose.
Is the machine in warranty? I

this may be due to fault in your display panel, check it by some hardware professional nearest to you

I wouldn't attempt as the capacitors on a tv store around 25000 volts this is more than enough to kill you and they keep there charge even when the tv is off. Either take it to a repair shop or put that money towards buying a new tv - Do not even attempt to open the tv. (It sounds like maybe a tube has gone or the electromagnet that makes the beam move vertically is gone.

Try reloading the drivers, delete the device in device manager and reboot. It should then pick up the drivers and reload them, if that does not work I would suspect the screen is on its way out (flickering normally means the screen or its connection is bad)