Computer components powers on but doesn't respond to the power switch and nothing really happens.

Check the memory and CPU are properly and fully inserted in their respective slots,sockets, etc.

Also check the video card is plugged in to its slot.

Is there a "PC speaker"? Sounds cards are cool, but before the PC has booted, only the motherboard beeper can be used to alert you to things like, no memory, no video card, etc. :-)

also check that your IDE cables are connected correctly, the red wire goes to pin 1, or remove them to at least see if the mobo boots. SATA cables can only go on the correct way round.

I hope that you didn't unplug the power from the motherboard with the system still plugged in, even if it was "off".

ATX systems are ALWAYS at least partially "on", even when they are shut down.  Before doing ANYTHING or plugging in or removing or unplugging ANYTHING, you must turn the power completely off.  That means use the power switch on the BACK of the power supply if there is one (there isn't always), or literally unplug the computer.

Start by disconnecting and removing everything except the CPU, CPU fan, memory and video card.  Disconnect all drives (hard, floppy, CD/DVD), both data cables and power cables (remove data cables at the motherboard).  Disconnect any added case fans or lights connected to the system, remove all cards other than the video card (no sound card, network card, or other PCI cards).  We are trying to elimate any possible source of a "short" or improper connection that could be causing problems.  Also, at this time, configure the motherboard with the minimum number of memory modules.

Then reconnect power to the power supply (plug it back on, and/or turn on the master switch if there is one).  If the motherboard has a light on it (most newer ones do but I'm unfamiliar with your specific model), it should light (even though the system is still "off") indicating power for the parts of the system that are ALWAYS on.  Don't ever work on the system while this light is lit.

Turn on the power.  Immediately, the CPU fan should start, the power LED light on the case should come on.  After a few seconds, ideally you should get a display on the monitor, you should hear the "POST" beeps and you should see the keyboard LEDs flash.

What I need to know to continue is what has happened at each stage as outlined above.

Assuming that everything happens but in the last step the system is dead (cpu fan does come on, but no POST, no video, no keyboard lights), there are a million things that can cause this.  First thing to check, is everything plugged in right and properly seated?  (remember, if plugging or unplugging ANYTHING, you need to kill the power).  How about the CMOS batter, some systems won't boot if it's not installed.  Are you sure that the CPU and memory are installed correctly?  Try removing the CMOS battery and resetting (clear) CMOS, then reinstall the battery.

I've seen a reversed mouse and keyboard (keyboard plugged into mouse socket and vice versa) cause a system to not post, double check that.  Actually, at this time, there is no reason to even have mouse at all, and you should get post beeps and some video with no keyboard as well.  So unplug both the keyboard and mouse and give it a try that way.

To check for a short, it is sometimes helpful to remove the motherboard and power supply from the case and try to power it up with no case, sitting on a non-conductive surface.  This is, however, a lot of trouble and kind of a longshot.

Be sure that there is not a jumper over the CMOS "clear" pins, I've seen this, and it will keep the system from starting up.

Try this, and let us know what happens.

I would try another power supply that you know works to see if it works , the test above that davchiu suggested is also a good way to test your motherboard. If neither using a new power supply or the above suggestion works then your motherboard is fried and I suggest getting a new one obviously. Would the cmos battery affect the computer starting up ?? If it is completely flat ??

Also dont you get any audible beeps ? If so your motherboard manual will tell you what they mean. If the suggestions we have suggested do not work then I would highly recomend calling your motherboard manufacturer, that is if it is still under warranty then you can see about a replacement, you could call them regardless though because I have read articles in computer magazines where they replace it for you anyway because of the manufacturer having a good repuation / customer support base.

Other then that just determine what component or components are at fault and then from there you can establish what you need to do :)

Make sure you have all the cables connected correctly because obviously if you do not have your cables from your graphics card to your monitor and the power cable from the monitor to the mains power connected correctly and firmly then it wont work in terms of seeing anything on screen :)

yes try another power supply and perhaps a little more powerful one. I think that should do the trick.

good luck

like a 400 watt PSU maybe or something around there :) plus or minus 50 watts :)

Here is some information that you might find usefull when trying to figure out if powersupply is powerfull enough for your PC

For your reference, following is a chart that illustrates approximately how much wattage you will need to run various common components in a PC system:

Component Wattage Required
Motherboard 15-30
Low-end CPU 20-50  
Midrange to high-end CPU 40-100  
RAM RAM 7 per 128MB  
PCI add-in card 5  
Low to midrange graphics board 20-60  
High-End graphics board 60-100
IDE hard drive 10-30
Optical drives 10-25  

He's not posting.  Power requirements will be minimal, neither the CPU nor video card would be doing much.  Even a GROSSLY inadequate power supply would turn on and you would see the initial post screens come up.  The only way that the power supply is he problem here is if it's bad, not merely inadequate.

My motherboard was fried. The video card and ram both worked in another computer. Went and got another of the mobo same kind and everything worked fine.

Thanks for all your help.