|Your symptoms cannot be caused by a software problem if the lines appear before Windows starts to load, or if when they have appeared , after rebooting they appear before Windows starts to load,|
AND your symptoms are probably caused by a hardware problem in any case.
If this is a laptop.....
- connect a monitor to the VGA port on the computer when the computer is off, and try the computer.
If the display on the external monitor is fine, then either
- the wiring between the base of the laptop and the display in the lid is damaged, most often right where it passes through the hinge.
In that casem the lines MAY go away when the lid is in certain positions, appear when it's in other positions That wiring is a commonly replaced item, not all that expensive, and a local place that is authorized to work on your brand can do that for you if you don't want to replace it yourself.
- the voltage inverter that supplies high voltage to the backlight is malfunctioning, although usually that won't produce your symptoms. The voltage inverter is relatively inexpensive, and relatively easy for a computer user to replace, if you're so inclined.
For either of those things, if you want to do it yourself, you'd be wise to get a service manual for your laptop to show you how to remove what you need to remove properly. E.g. HP, Compaq, and Dell models often have one on the brand name's web site (HP supports Compaq) you can download for your model or model series. For other brands they may not have that and you'll have to search the web for one, and you may have to pay a fee online to buy it.
(these can also apply if the external monitor does not produce a normal display)
- the display assembly or the computer otherwise is damaged,
- most commonly from you or someone else dropping the laptop,
- or from you or someone else spilling liquid on it and some of that got inside the laptop while the computer was running, or it was not running but that was not cleaned up before the laptop was powered up after that (it doesn't matter if it was running at the time or not at the time - the mboard is always powered in some places as long as the main battery is installed).
If this is a desktop computer......
- unlikely - if you are using a LCD monitor, the voltage inverter on it may be malfunctioning - see above - it that case you'll get the same symptoms on that monitor if you connect to any computer, and another computer monitor connected to your computer will work fine.
- your power supply may be malfunctioning, but if it was it's not likely it would produce your symptoms.
Failing power supplies are common and can cause your symptoms.
Check your PS.
They often partially work, fans and hard drives may spin, leds may come on, yet you may get no video and the mboard will not boot all the way.
See response 4 in this:
If it is failing, you can usually replace it with any decent standard sized standard ATX PS with the same capacity or greater.
Standard (PS/2) power supply size - 86mm high, 150mm wide, 140mm deep, or 3 3/8" h x 5 7/8" w x 5 1/2" d , or very close to that, though the depth can be more or less for some PSs.
Don't buy an el-cheapo PS.
See response 3 in this:
Your power supply must have at least the minimum capacity required to support a system with the graphics card you are using installed, or the max graphics card you might install in the future.
(Onboard video - video built into the mboard - IS NOT A CARD!)
You can go to the video card maker's web site and look up the specs for the model - often under system requirements - the minimum PS wattage, and, more important, the minimum amperage the PS must supply at 12v is stated. If you don't find that, any card with the same video chipset including any letters after the model number has very similar minimum PS requirements.
- your video card installed in a slot may have a poor connection (onboard video - video built into the mboard - IS NOT A CARD!)
Unplug the case/power supply.
Power off your monitor.
Open up the case by removing the left panel as seen when you're looking at the front of the case.
Check all the connections of the wiring to make sure they are all the way onto their pins and into their sockets, especially the main connector from the power supply. The wires close to the mboard going into the main power connector/socket should be more or less perpendicular to the mboard surface rather than at an angle. Most mboards and some video cards have an addtional socket a connector from the power supply must be connected to (other than the main connector to the mboard). Make sure all cards in slots are all the way down in their slots. If in doubt, remove the card, install it again.
Your symptoms can also be caused by the cpu (processor) overheating. In that case the display is probably fine when the computer has been booted after having had a chance to cool to room temp while booting and for at least a short while after that, then you get the video symptoms.
While you're in there, if the cpu fan/heatsink has mung (dust, lint, etc.) on it, clean it off, but DO NOT use a vaccuum cleaner to do that (they produce a tremendous amount of static electricity when running, and anything connected to them can discharge that to your components) - use canned air, or an air nozzle if you have access to an air compressor, or an artist's brush that can be used in small spaces, etc. It may be difficult to clean the top of the heatsink under the cpu fan - the most likely place to have mung on it - and the bottom side of the cpu fan blades unless you remove the fan. If you have a case fan, clean that too if it needs it.
With the cover still off, restore the AC power, start the computer and make sure the cpu fan spins - if it doesn't spin, if you're sure the power supply is working okay, don't use the computer until you have replaced it.
If it spins too slowly, and/or if it makes rattling or screeching noises, most likely to be noticed when the computer has cooled to room temp, has not been used for a while, and then is started up, the cpu fan's bearings are failing - replace it as soon as you can.
If the onboard video - video built into the mboard - is what you are using, if the power supply is okay, the mboard is probably damaged!