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.)