Dual Monitor suddenly lost the second monitor

I've been using dual monitor setup for a years now. But today , out of the blue, I lost the second monitor just after logging in to  windows XP.

I notice that prior to login screen, the monitor is actually still operational. The bios screen is displayed on both monitor as it always does. Which means it shouldnt be a hardware issue.

I tried "enable second monitor" on display properties, but when I click the apply button, the box would revert back to being unticked. Also doing that causes me to lose my desktop background to a dark blue background. WHen I'm logging off though, I would see my original desktop background for a few seconds.

I tried system restore to a few days ago, but it doesnt help.

On event viewer, I noticed an warning: userenv, Event ID: 1517 with this message:
"Windows saved user COMPNAME\USERNAME registry while an application or service was still using the registry during log off. The memory used by the user's registry has not been freed. The registry will be unloaded when it is no longer in use. "

And because of that I tried the microsoft Hive tool (UPHClean-setup.msi), which doesnt help. The registry would say that it has been unloaded, but the problem persist.

Short of reinstalling the driver (I'm always suspicious that doing that kind of t hings would cause further errors, besides I cant remember the type of card I'm using. I only know its an ATI.)

Thank You
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There is a very good chance there is a problem with the driver. Have you tried downloading and installing the newest driver for the video card?
HainKurtSr. System AnalystCommented:
turn off everything, check plugs... turn on, play with "display properties - settings", click identify, set one primary

if it does not help, click advanced, go to ATI Catalyst properties and there should be more settings and wizards to play with... if it does not help, you may need to reinstall (latest or the one that you use) ATI driver...
I'm not sure of losing your dual-screen and how to resolve, but if you need new drivers see below.

To verify you are obtaining the proper driver go to Device Manager and select your display adapter then go to the Details tab - If not defaulted  - go to Device Instance ID and write down your information if it's not displayed at the top.
mine is:
    pci\ven_10DE&DEV_00CD&SUBSYS_029B10DE&REV_A2 etc...
when googled "pci\ven_10DE&DEV_00CD" I get several results regarding the "NVIDIA Quadro FX 3450/4000 SDI" which can be sorted to help determine the card.  The more you can put in and get results the closer the match and less to sort through. Generally looking at the PC vendor or card manufacturer "ATI" will be your most reliable sources.
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ATI has their own tool, which allows you to enable te second monitor as well, you can download it here:
SW111Author Commented:
Well, tried re-installing the old driver but problem is still there.
Now trying to download the newest version. Turns out its an ATI x1900 series.

Not sure why I need to do this since its been working for years though...
Will update as soon as I'm done with downloads. Thanks you.
SW111Author Commented:
I tried installing the latest driver, but was not successful. The problem is still there.

HainKurt: the second display is working during bios and not after login screen shows. I think it has something to do with the software.

I have had the same thing happen with one of my retail pos computers, also an ATI card. First, after reinstalling the driver, make sure that the option for enabling dual monitors did not come unchecked.

Also, due to the the tight location on my computer, one of the cables has a loose connection and has to be screwed down tightly or it loses signal. One way of testing for a good connection is to switch the two video cables.
SW111Author Commented:
Barnasea, Thanks for the reply. No, the dual monitor is unchecked but I cannot check it (After checking it and clicking align, nothing happens).

I'm quite sure its not the hardware (including cables, etc) simply because botmonitor would display the BIOS screen.

In fact, if I uninstall all drivers and anything ATI, and run the computer without a display driver, then both monitor would display the same image (a clone). But on display property there'd be only 1 monitor
I agree that this does not look like a hardware issue, and the clone mode is obviously the hardware default mode for the card. That means the issue is either OS or driver.

After you install the driver, are you able to see all the resolution modes that you used to have? Are you able to set it to 32-bit color and change the desktop image, or is it stuck with the blue background you described?

Assuming there is a driver or setting problem, a more methodical approach to installing the driver may help. For instance, uninstall anything from ATI from add/remove programs, and uninstall any display drivers from device manager, and reboot the computer. Install drivers and reboot again.
SW111Author Commented:
Yes, the resolution I normally use is still there, although strangely enough, they display different options. There are actually many more options for monitor 2 then for monitor 1.

32 bit for both monitor were automatically set and yes, I can change the desktop background to the standard windows options. BUt not to the custom walpaper (jpeg) that I originally have.

Yes also to uninstall and reinstall everything ATI. DOne that but problem persist....

Event Viewer is not showing any warnings or errors anymore.
The reason for the different display options is that the card detects the supported resolutions of the monitor; not just the ones that look right, but all of the ones that will allow display.

Personally, I would be tempted to switch to a card from the other manufacturer (nvidia). Not to say there isn't another solution, but changing cards means a whole new driver set.

If you had a backup image, you could restore to a different hard drive. If not, just reload the OS from scratch, or run a repair. Not to say these are the only solutions, but they are likely to resolve the problem.
SW111Author Commented:
Ok. SO I've found a solution:

I've tried turning on and off, plugging and replugging, driver install, uninstall, reinstall and most of the recommendations here and nothing had worked. And then I found the above solution.

The solution turns out to be:
1. Unplug both monitor cables (both ends: monitor and cpu side)
2. Unplug power cable for both monitors and the cpu.
3. here's the trick: WAIT for a long time. In my case, I left it for 2 days and 1 night.
4. Replug everything and turn on computer.

It worked as if nothing had ever happened.... Amazing.

It turned out to be a hardware problem afterall. Only in this case, perhaps its some kind of memory or static electricity that's troubling the system. The weird part was that it always displayed dual monitor in BIOS and single monitor once we get into windows. It made me think it was a driver issue....

BUt Thank You banrnsea for your attempt to help.

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If you genuinely feel that none of the suggestions led you to the solution, then it is fair to close the question without accepting a solution. However, I would point out that both Hainkurt and I pointed out that you should disconnect cables and check for loose connections.

In my experience, leaving equipment powered off for awhile can correct an overheating issue, but only temporarily, and will recur next time the system is under heavy load. But just because I have never used that solution to fix a problem like yours, does not mean it didn't work.
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