This is to see if one monitor of the two monitors is failing or its internal settings are locked up/messed up. If you get both monitors to work as normal single monitor, try swapping your now mon1 and mon2. I think you have a monitor problem not a driver problem. If you have another monitor or a friend's try swaping out with the monitor that is not working.
My GeForce FX 5500 eVga card was running dual monitors just fine, but suddenly the second monitor went blank ("No Signal"). I uninstalled the Video Card driver from the Device manager and nVidia drivers from "Add remove programs". Then booted into Safe mode and reinstalled the forceware drivers for XP. (94.71 - latest version). Didnt work. I tried this several times, it doesnt work.
During the boot process, the second monitor works fine until Windows loads, then goes blank ("No Signal"). The second monitor also works in Safe mode and when I uninstall the GeForce FX 5500 Video card Display Adapter from the Device manager. So its obviously a Video card Display Adapter issue.
Note I can see the second monitor in Device manager and also in the Display settings. "Extend my desktop to this monitor" is visible and can be checked, but as soon as I do that the second monitor blinks once and says "no signal".
I did try to enable "Auto-Select" on Full Screen mode in the Display settings Advanced tab GeForce tab, but this has the same effect (the second monitor blinks once and says "no signal").
I dont know what to do - I need the 2nd monitor. This was working fine, and has suddenly stopped!
Using Windows 2003 Server, Samsung 17" LCD TFT (1st display) and Hyundai 17" LCD TFT display (2nd display) with DVI-to-VGA adapter.