|If you haven't been fiddling inside the computer case, haven't changed which ram you have installed, and if the computer was not been moved from place to place, or if it's a laptop, it hasn't been dropped, since it last worked properly, the most likely things are|
- there is a problem with the connection of the ram to it's slots.
See response 2 in this - try cleaning the contacts on the ram modules, and making sure the modules are properly seated:
For a laptop, or netbook, you must remove both its main battery and AC adapter before you do that.
For a brand name computer, see the Owner's or User's manual if you need to - how to remove or replace the ram is usually in that - it may already be in your installed programs. If you can't get into Windows, it may be on a disk that came with the computer, or you can go online and look at it or download it - it's in the downloads for your specific model.
For a generic desktop computer, see the mboard manual if you need to - how to remove or replace the ram is usually in that.
- if it's a desktop computer, your power supply may be in the process of failing.
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.
You often have intermittent problems with booting the computer for a while before you can't boot at all.
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 ! )
If that info is not in the ad for the video 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. Some power supplies have two or more +12v ratings - in that case, add those ratings to determine the total +12v current capacity.
If you're a gamer...
In most if not all cases, the max capacity rating of the PS is an intermittent rating. It's recommended that you do not load your PS to any more that 80% of that rating if you are going to be using something that puts a constant load on it, such as playing a recent game for hours on end. In that case, you multiply the min capacity stated for the system with the particular video chipset on the card by 1.25 to find the min. capacity of the PS you should get.
If you need to get a PS with more capacity, you can usually replace it with any decent standard sized standard ATX PS.
Power switches on desktop computers are extremely reliable, it's very rare for them to malfunction, but
- sometimes the case button that presses on them can stick inwards, and in that case, if that is keeping the power switch on, the mboard will shut down within a few seconds, depending on bios settings, but usually that's the situation. The same thing will happen as when you hold the power switch button in.
- if there is a loose connection of the case wiring from the power switch at the end connector where it plugs onto the 2 pins for that on the mboard, pressing the power switch may be unreliable. That's not likely.
If the case has a Reset switch, on ATX cases, the power switch and reset switch are the same type - momentary contact, on only when pressed in.
You could try connecting the Reset switch wiring connector to the Power switch pins on the mboard, and use the Reset switch as the Power switch, but there's probably nothing wrong with the Power switch.
If there is no Reset switch, or if you want to try something else, if you remove the wiring connector from the pins for the power switch on the mboard, and briefly, carefully short the power switch pins, the mboard should boot fine if nothing else is wrong.