FSX stuck in demo mode after reinstall; no prompt to enter product key/activate

Roy / Jacek,

Don’t go hunting random “clean DLL downloads” for MSXML. That’s a fast way to end up with a compromised system, and it usually doesn’t fix FSX activation anyway.

What typically causes the “no product key prompt / stuck in demo” behavior is either (a) the activation components never ran properly, (b) permissions/UAC blocking the licensing write, or (c) leftover licensing data from prior installs confusing things.

Step-by-step things to try on Win 11

1) Install order (important)
If you haven’t already, do it in this exact order:

1. Install FSX Deluxe (base sim) and run it once.
2. When FSX launches the first time, it should ask for the key / activation. Complete it if it prompts.
3. Only after that, install Acceleration.

If Acceleration is installed before the base sim gets its activation sorted, you can end up in this loop.

2) Run the installers “as Administrator”
On Win 11 this matters more than people expect:

1. Browse the DVD and right-click setup.exe (FSX) -> Run as administrator.
2. Same for the Acceleration DVD setup.exe.

3) Compatibility mode (worth testing)
Right-click the installer -> Properties -> Compatibility:

• Try Windows 7 compatibility + “Run this program as administrator”.

Do the same for the FSX shortcut the very first time you run it.

4) Don’t manually register “msxml4.dll”
Acceleration not “showing the activation window” is almost never solved by registering a random MSXML DLL.
If MSXML is genuinely missing/corrupt, you fix it by installing the proper Microsoft MSXML package (not by copying DLLs around). Also, the filename you typed (“msxmi4.dll”) looks like a typo, which makes me think you’re chasing the wrong thing entirely.

5) Clean reinstall (if you’ve already tried multiple times)
If you’ve been uninstalling/reinstalling repeatedly, you may need to clean out leftovers:

1. Uninstall FSX and Acceleration from Windows “Apps/Programs”.
2. Reboot.
3. Delete the remaining FSX folders (if they’re still present) under your FSX install location and the usual profile locations.
4. Reboot again.
5. Reinstall using the order in Step 1.

(If you want, tell me where you installed FSX to and I’ll tell you exactly which folders to check.)

A few targeted questions so we don’t guess

1. Is your FSX Deluxe + Acceleration the original DVD set, or the Steam Edition (FSX:SE)? (Activation works differently.)
2. At what exact point do you end up in “demo” — immediately on first launch of base FSX, or only after Acceleration is installed?
3. Do you get any error message during install or first launch (even a brief one)?
4. Where did you install FSX (example: C:\Program Files (x86)\Microsoft Games\Microsoft Flight Simulator X or somewhere else)?

Answer those and we can pin down whether this is an install-order issue, permissions/UAC, or a broken activation component.