Gateway GX7018E / T6420 = swap video cards for a test?????

This model Gateway desktop computer has a built-in video card.
Connect the monitor to the Gateway motherboard video port and the boot up and go into the BIOS and select disable the built-in video.
Shut down then connect the monitor to the 8800GTX video card and boot up the Gateway computer. The video should then appear in the monitor.

Do you have another monitor or TV with dvi/hdmi? Try to see if that works. And it seems like you changed the graphics output while in Windows. Try turning it off, swapping the cable and turn on again.

Sounds like there is an issue with the video card settings versus your monitor.

Try the following:

1.) Press F8 on boot and select VGA mode then once into the OS reset the video card options

2.) Try another monitor

3.) If you have video card, swap it out. If you have onboard graphics put a card in

Cheers...please post your results.

This is eMachines Support, T6420 desktop computer>Specifications, and downloads page for the User Guides,

http://www.emachines.com/support/product_support.html?cat=Desktops&subcat=T%20Series&model=T6420

The eMachines T6420 does not come with a graphics card from the factory.
It comes with Integrated Graphics.

Integrated Graphics is also known as OnBoard Graphics.
On the motherBoard

The GPU is soldered to the motherboard.
(Graphics Processing Unit,

http://en.wikipedia.org/wiki/GPU

OR,
someone has installed a graphics card, into the PCI Express x16 slot on the motherboard.

You can determine real easily if your computer is using Integrated Graphics, or a graphics card.

If it is using Integrated Graphics, the monitor will be plugged into the I/O area, on the back of the computer, and into a VGA port,

http://en.wikipedia.org/wiki/VGA_connector

(I/O area;

I/O = Input/Output

The I/O area, is the area that has the rectangular metal shield, and Input/Output devices are plugged into this area.

Devices such as a Keyboard, Mouse, Printer, and so on )

HOWEVER, with the motherboard used in an eMachines T6420, the I/O area could also have a white DVI port.

http://en.wikipedia.org/wiki/Digital_Visual_Interface

This was an option offered. The DVI port still connects to the Integrated Graphics on the motherboard.

The eMachines T6420 uses an MSI MS-7207 motherboard.
(Micro Star International, Inc.)

http://www.tigerdirect.com/applications/searchtools/item-detailsInactive.asp?EdpNo=2665522

The above link is to,
1) Show the motherboard
2) Provides a link to the Motherboard Manual

Looking at the photo of the motherboard, you will see two long White slots.
Above these two slots you will see a longer White slot.

The bottom two white slots are PCI expansion slots.
The top longer slot is a PCI Express x16, expansion slot.

This is where a PCI Express graphics card would go.

I would like you to scroll to the bottom of the page, to the Product Resources heading.

Under it is a link to the Motherboard Manual, for the MSI MS-7207 motherboard.
Also known as K8NGM2-L

Left-click on the blue - MSI K8NGM2 Series Manual.

You will be looking at a blank white page, as the PDF file downloads in the background.
Took 34 seconds with a medium speed DSL connection, for me to download it.

NOW,
No Signal on the monitor, means the monitor is Not receiving a video signal.

1) Check the monitor cable if it is removable. Use it on another working computer to insure it is good.

2) If the monitor cable proves to be good, the next area to check would be the graphics.

If the computer is using Integrated Graphics, and no one has installed a graphics card, the test would be to install a graphics card, and plug the monitor into it.

Computer off, unplugged from power, Anti-Static precautions are observed before reaching inside the computer, and handling the graphics card.

I don't think the problem is the graphics. Could be wrong, but we'll see.
Let's carry the diagnosis past the graphics for now.

I think the problem could be due to a bad Power Supply.
Weak Voltage power rail.

Enough power to light lights, and spin fans (Perhaps), but not enough to turn the Processor on.
(Fans may be spinning, or may just spin a few times, and stop)

1) ALL the lights use Less than 1 Watt of power
2) EACH fan uses 2 to 3 Watts of power.

3) A typical Processor can use 51 to 125 Watts of power.

Continued in an additional Comment.

I would check the BIOS To check the boot order preference to see if you can tell the motherboard to Force Starting up with the PCI-E Slot.

If the slot did go bad, most likely you would see the system crash instead of just automatically going back to using the onboard video card.

Your video output is bad. Either the video card, or the onboard video built into the computer. You need to swap out the card or add a card to bypass the built in video port on your computer.

Thanks and please take a moment to rate as fixya.

I think ur power supply SMPS inside the systemneeds to be replaced...

Most likely your video card is broken. To check if the motherboard isnt broken either, I would suggest you test usb, sound, and other features of the motherboard.
 If your motherboard isnt broken then you have to buy a "pci-e graphics card" at your local store. Shouldnt cost much, about $40-70. Hope that helps.

That's exactly what it sounds like. I would put in a new video card (or used one, if you have one) into one of the expansion slots and run it from there.

I would suggest to go into VGA mode just to make sure, but since your monitor never even gets off standby, I'd be 99% it's the onboard video.

Hope this helps!

You can put new Video card accordingly. Just buy an good Video card which have inbuilt memory and that support your operating system. There are loads of Video card available in the market.