If your laptop does not start at all or it starts but will not boot properly, it¡¯s possible that you can fix the laptop at home without taking it to a repair center. Here are some troubleshooting tips for you. I¡¯m not sure if I can cover all situation at once, so I will update this post as more examples come into my mind.

Situation 1.

The laptop appears to be dead. You plug the AC adapter but the LEDs (power light, hard drive light, battery charge light, etc¡­) do not light up and the laptop will not react at all if you press on the power button.

First of all in this situation check the AC adapter. You can test the output voltage with a voltmeter. If you cannot do that, find a known good AC adapter and use it for testing the laptop. It is possible the laptop appears to be dead because the AC adapter is bad (and the battery is discharged). If you know that the AC adapter is working properly and it outputs correct voltage but the laptop is still dead, most likely you have a power issue on the motherboard (or power board on some laptops) and it has to be replaced.
If you have to replace the AC adapter, make sure you use a correct one. The output voltage must be exactly the same as on the original adapter. The output amperage has to be the same as on the original adapter or higher, but not lower.

Situation 2.

When you plug the AC adapter the power LED and the battery charge LED light up. When you press on the power button the laptop powers up but will not start. There is no video on LCD or external monitor.

If the power LED lights up it indicates that the laptop is getting power from the AC adapter. Most likely there is nothing wrong with the adapter but just in case test it with a voltmeter to make sure the output voltage is correct.
Also try this. Unplug the AC adapter, remove the battery and wait for 1-2 minutes. After that plug the AC adapter ans try starting the laptop again. Sometimes this trick helps.
It also could be a memory related problem. Try reseating the memory module, just remove it from the slot on the motherboard and install it back. Try installing the memory module into the other slot (if it¡¯s available). If you have two memory modules installed, try removing them one by one and start the laptop just with one memory module installed.
If the laptop starts fine with one memory module in both slots, but will not start with the second memory module in both slots, the second memory module is faulty. Replace the module.
If the laptop starts fine with both memory modules when they are installed in the slot A, but will not start with both memory modules installed in the slot B, the slot B is faulty and you¡¯ll have to replace the motherboard or use only one memory slot.

Situation 3.

When you press on the power button, the laptop makes a series or short and long beeps and will not start up. There is no video on the screen.

In this situation test the memory module as I described in the situation2. Try installing a known good memory module. Most likely you are getting a beep error because of a faulty memory.

Situation 4.

You start the laptop. It sounds like the laptop is booting normally (hard drive LED is flashing) but there is no video on the screen

In this situation test the laptop with an external monitor. If the external screen works fine but there is no video on the laptop LCD, most likely there is a problem inside the laptop display assembly. Go to my previous post witch covers laptop video problems in more details.

Situation 5.

You start the laptop and it starts making repetitive clicking noise or grinding noise.

Most likely you hear this noise because of a faulty hard drive. You can remove the hard drive and start the laptop without it. If the noise is gone, the hard drive is your problem. Replace it.
If the laptop makes clicking or grinding noises and you still have video on the screen, you can run a hard drive test utility. I usually use Hitachi¡¯s drive fitness test. This test is reliable and easy to use.

Situation 6.

The laptop boots into Windows ans works for a while, but after that it shuts down by itself without any reason or warning. You restart the laptop but the same problem appears again

Most likely it¡¯s a heat related issue. Listen for the cooling fan, make sure it works.
Also this problem might appear because of a faulty memory module, try some tips from the situation 2.
The laptop still boots ans you still can see the screen, so you can run the memory test. I usually use Memtest86+. Run the memory test and if it fails, replace the faulty module.

Situation 6

The laptop starts normally but video on the screen has lines, some strange characters or other defects

It could indicate a problem with the laptop LCD screen, video cable, graphics card or motherboard. Here¡¯s my previous post witch covers troubleshooting bad images on the screen in more details.