Hi, My 4 year old Gateway desktop is on 24/7, then one day I got home and it was off. I tried starting it, but only the on light came on. I tried a new power source, then a another mother board, but still nothing. There is a light on the mother board that illuminates when the computer is plugged in. When I hit the start switch the light comes on but nothing happens, if I press and hold the switch the light goes out after a few moments as it would once the computer would have shut down. I've checked and rechecked the connections, I don't see any obvious problems. Do you have any ideas? My last option is to bring it somewhere because of the expense just to bring it in. Thanks.
Does the fan come on or just the light?
It sounds like a bad motherboard. Check to see if you have any broken or leaking capacitors. If you aren't familiar with what they look like, they are the cylinder looking objects that stick up all over the motherboard. The tops should all be perfectly flat. Any bulging or leaking means that they are broken. If they are leaking, don't touch the stuff as it's not real good to get on your skin or in your eyes, etc.
You could also just have a bad power-supply motherboard, fan or CPU or any number of bad parts that have no physical symptoms caused by normal wear and tear or an unexpected power outage.
If the computer is 4 years old, I don't recommend paying too much to get it fixed.
I had a machine go bad on me and went to a local computer store and bought an external USB HDD connector device for about $20. You can use that to plug your HDD into another computer via the USB port and copy your documents, photos, favorites and any other files you want to keep (your programs will need to be reinstalled, but you can keep some data files / saved games out of those programs if you know where to look for them).
If you decide to use that USB HDD device, you must follow the instructions for using it and only plug it in while the computer is turned off, just to be safe. I had an older computer lock up and crash completely when I tried to just plug it in while everything was turned on. It was XP so I had to roll back to a restore point to get it to boot again.
I tried another power supply and motherboard with no change, so I'm assuming they aren't the problem. Is there a way to check the power switch, or any other ideas? Thanks.
Assuming that the new power supply and motherboard are both working, try to remove all peripheral devices and see if the machine powers on.
All devices being floppy, CDROM, HDD, any USB devices, PCI cards (including video), and memory.
If the machine powers on and all the fans start moving, one of those devices is the problem. Of course, you will get beep codes telling you that you are missing all that stuff you just took out, but add them back in 1 at a time starting with the memory until you find the problem.
Barring all of that, if it still doesn't power on, I would suspect the power switch cables are not plugged in properly, the fan is not plugged in properly on the motherboard or the CPU and / or fans are bad.
If you have a fluke, you could test to see if your CMOS battery is dead too. :)
I suppose the power switch could be bad, but since you said you push it and get a light on the case, I am assuming that the mechanics of the power switch are in full working order and the problem is electronic or electrical.