PMDG 737NGX crashes FSX:SE when loading or after spawning

First thing I would check is the source/install

Roberto, the important clue is this part:

PMDG_737NGX.dll

That file is not just a display gauge. It is one of the core NGX modules. If removing it lets the aircraft appear, then FSX itself is probably not the main problem — the crash is occurring when the NGX systems module is being loaded.

The other big issue is the Internet Archive copy. The PMDG 737NGX was a commercial product and really needs to be installed from a proper PMDG installer tied to a legitimate license. Random archived copies can be incomplete, modified, missing registry entries, missing activation components, or simply not the correct installer for your FSX/FSX:SE setup. I would not try to troubleshoot that copy too deeply, because you can chase your tail for hours.

What I would do

1. Remove the NGX completely from FSX:SE.

   Check the aircraft folder under:

   ...\FSX\SimObjects\Airplanes\

   and remove the PMDG 737NGX folders if they remain.

   Also check:

   ...\FSX\Gauges\

   and remove leftover NGX gauge/module files only after uninstalling.

2. Start FSX:SE once with a default aircraft, preferably the default C172 or default 737, and confirm FSX is stable.
3. If you own the NGX, reinstall it using the original PMDG installer for FSX/FSX:SE. Run the installer as Administrator.
4. Start FSX:SE with a default aircraft first. Once the sim is fully loaded at an airport, then change aircraft to the NGX.
5. If FSX asks whether to trust a PMDG gauge/module, allow it.

A few other things worth checking

• Make sure FSX:SE is not installed in a protected Windows folder if possible. Older FSX add-ons often behave badly when they cannot write to their own folders.
• The MD-11 and 747 working does not necessarily prove the NGX is good. Each PMDG aircraft uses its own modules, and one aircraft can work while another fails immediately.
• The click sound is probably just the last sound triggered before the gauge/module crash. I would not read too much into that by itself.

Get the actual crash module

Please check Windows Event Viewer after the crash:

1. Open Event Viewer.
2. Go to:

   Windows Logs\Application

3. Look for an error at the exact time FSX crashed.
4. Copy the faulting module name and exception code.

If it says the faulting module is:

PMDG_737NGX.dll

then that strongly points back to the NGX install/module itself.

Questions

• Do you own the PMDG 737NGX and have access to the original PMDG installer?
• What exact FSX:SE version/build are you running?
• What does Event Viewer show as the faulting module?
• Is FSX:SE installed inside Program Files, or somewhere outside it?
• Do you get any PMDG activation/trust prompt before the crash, or does it die immediately?

My honest view: if this is only the archived Internet Archive copy, I would stop there and get a proper installer. The behavior you describe is exactly the kind of thing I would expect from a broken, incomplete, or non-original install of a complex PMDG aircraft.