I assume that, like most, it boots up in one resolution and then as the OS loads it changes to whatever resolution you want. If so, you are looking at the possibility of LCD, video hardware, or video memory issues.

Changing the resolution in the OS might give you an indication on where the trouble lies. Using a program like paint should allow you to change the colors in that area to see if it reamins as a hardware issue.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

Ed Fair
You are right. I don't change the resolution (1920 X 1080) BUT I do change
"Make text & other items larger or smaller"
From SMALLER 100% to MEDIUM 125%
and when this change happens, the dark spot appears.
Again, is their a fix that I can work on?

How about refreshing the desktop? Might overlay the right colors.

I probably would reset the resolution to the next step down that displays correctly and see if that helps.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

Edfair
I used paint and it made no difference to the dark area on the screen.
I tried changing from 125% to 100% screen size with no change.
I fear this is a "motherboard" problem ?

I would suspect that it is a graphics chip problem.

What OS? And when you changed to 100% what was the resolution that it was displaying?

Ed Fair
Give the wrong symptoms, get the wrong solutions.

I would download a linux live cd, and burn it, and boot from it, that will eliminate if it is a software issue or not. If you still have the dark spot it will be hardware, and really there are several possibilities as to the issue. As it is an all in one, it will use the ram as video memory, and the cpu actually has the video chip integrated into it. It could be the lcd inverter card, or the lcd itself. or the power supply is weak, and not supplying enough power to run everything. So to help eliminate them try this if it occurs with the live cd, it is hardware. Try running a monitor or tv from the video out, does it have the same issue? if so you can rule out LCd, and Inverter card. If not, then look to those, with the obvious choice being the Inverter card, first as it runs about 25-50 dollars, compared to a LCD with a bulb or led set going bad. AIO computers generally use a desktop cpu, but can have a mobile chip, This has a desktop I3-2120 But it has laptop sodimms for memory, it could be either at this point, look at youtube video on how to get back cover off, your unit has 6gb ram, so it has 1 4gb and 1 2gb dimm, remove one of them and boot it up to see if issue still there, if it is, swap it with the other dimm, is it still there? if it is, at this point it is either the power supply or the the cpu/gpu, and at a guess I would lean to power supply as cpu's rarely fail without something like a heat issue or a power spike. If you get lucky and the live disk doesn't show the issue, look at updating the video drivers, get those from Intel and not from gateway, because gateway drivers will be down level, they always are.

Well, I got the back off....what a job!!
I am using Windows 7.
I removed a 2GB memory card but I don't think it made any difference because:
The dark spot now has a life of it's own. When it appears, it does diminish the entire screen to some degree.
Now....the computer boots up and no dark spot is present!
After a minute or so (I think something is heating up) the dark spot appears.
Later .... the dark spot (something is cooling off) SOMETIMES will disappear and the screen is again normal.
So, I have an intermittent dark spot that comes and goes at will....very frustrating.
Question:
Does my dark spot illustration above RING any bells as to the cause OR am I still faced with multiple possibilities?
PS
It has taken me at least 30 minutes to compose this article and for the entire time my computer screen is FINE.....this computer is laughing at me!
Thanks for any/all opinions.

The intermittent come and go would normally be a flag for the graphics chip with those systems I have worked with. The diminished screen is typical of a power drop along a trace or across a connector.

Welcome to life in the intermittent world. The worst one I fought to the glorious end was 3 months (intermittent work) to resolution.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

I would still hook it up to another monitor or tv to see if it is on both screens when the spot is there, if not, then it is either the lcd convertor card or the lcd panel itself, and the only way to know for sure is to swap one of the parts out.

Gentlemen,
I appreciate all the help/suggestions given.
Within the next two weeks I will have another Gateway One ZX6971 computer that I can use for parts and will try excanging the converter card.
I will connect the computer to my 48" Sony LCD tv BUT I have to go to school on the hook-up process for this setup.

Everything takes educational time AND all I want to do is use my computer!

Both of you have saved me time pointing me in the right direction and I will let you know later the result. Thanks again.

The symptoms sound as though a program (not supplied by Gateway with the OS) is choosing to write in the memory block that is being used for the video. If you've added any 'helper apps' besides regular Office productivity tools, try removing them and see if the problem disappears. Or it could be malware/spyware that you didn't load, but has crept in....

Fred Wagner
(retired, but still involved!)