FSX Multi-Monitor Display Issue: Aspect Ratio and Resolution Anomalies on Auxiliary Screens

Having sunk many hours into tweaking and resolving various glitches with FSX, I empathize with your predicament. It can be a tad frustrating when you feel you're retracing steps you've successfully undertaken before. Nonetheless, let's dissect the situation.

1. Display Configuration within FSX:
The first port of call is to verify the Display Settings within FSX. Here’s a quick rundown:

• Navigate to the Settings tab.
• Proceed to Display.
• Under the Hardware tab, ensure your Target frame rate isn't set too high. Aim for around 30 for optimal performance.
• Under Graphics, make sure the Global texture resolution is set to Very High.
• Now, hop over to the Aircraft tab and see if the High-resolution 3D virtual cockpit is checked.

2. Graphics Driver Check:
Windows updates have a notorious track record of causing a few hiccups, especially with graphics drivers. Reassess your GPU drivers - sometimes, reverting to a previous stable version can miraculously rectify issues.

3. FSX Configurations:
Delve into the FSX.cfg file (usually found in the AppData\Roaming\Microsoft\FSX directory). Look for the DISPLAY.Device section. Ensure the Mode setting matches your desired resolution and aspect ratio. For instance:

Mode=1920x1080x32

Adjust accordingly for each monitor, remembering to back up the original file beforehand.

4. Monitor Calibration Tools:
Sometimes, third-party monitor calibration tools can interfere. Do you have any running? If yes, try disabling them and see if FSX behaves better.

5. FSX Display Window Mode:
Running FSX in windowed mode occasionally provides better compatibility with multi-monitor setups. Toggle between full screen and windowed mode (usually by pressing ALT + ENTER) to see if it influences the aspect ratio and resolution.

Lastly, just a thought – I know you mentioned this issue pertains solely to FSX, but it might be worth peeking into your Nvidia Control Panel or AMD Catalyst Control Center (depending on your GPU) to double-check your global and program-specific settings.

Hope this helps. Dive in, and should you have further queries or require elaborations, do let me know. We're a community here, always ready to assist. And if anyone else has faced and conquered this particular dragon, their insights would be invaluable.