FSX Deluxe + Acceleration on Windows 11: activation window won’t appear (missing MSXML4)

Roy,

You don’t want to go hunting random DLL downloads for this. Apart from the security risk, it usually doesn’t actually fix FSX activation on modern Windows because the activation UI relies on more than just one file.

Also, small but important correction: the file is msxml4.dll (Microsoft XML Core Services 4.0), not “msxmi4.dll”.

What I’d try first (safe + usually works)

1. Make sure FSX Deluxe (base) is fully installed and started once before touching Acceleration.
2. Right-click setup.exe on the FSX/Acceleration discs and choose Run as administrator.
3. Temporarily disable any “Controlled folder access” / ransomware protection in Windows Security (that feature can block the licensing/activation components from launching properly), then try the activation again.
4. Install outside Program Files if you can (example: C:\FSX\) to avoid UAC/file-virtualization weirdness.

MSXML4 specifically
Acceleration did commonly install prerequisites, but Windows 11 won’t always accept older bundled installers the same way Windows 7/8 did. The correct fix is to install MSXML 4.0 from Microsoft’s installer package, not to manually drop in a DLL from some site.

If you already have MSXML4 on the machine and it’s just not registering correctly, the only “manual” step I’d consider is re-registering the existing DLL (again: only if it’s already present on your system, not downloaded from a random place).

A few targeted questions so we don’t chase the wrong thing

• Is this the original boxed/DVD FSX Deluxe + Acceleration, or Steam Edition?
• Does the base FSX Deluxe activate/launch fine, and only Acceleration won’t activate? Or does neither activation window appear?
• When you try to activate, do you get any error message at all (even a brief popup), or does it simply do nothing?
• Where did you install FSX to (full path), and are you running the installer as admin?

Answer those and I can steer you to the cleanest fix for your exact case (there are a couple different failure modes on Windows 11, and they look similar from the outside).

Roy,

That helps a lot. Since base FSX activates and runs, we can stop chasing “general FSX on Win11” issues and focus specifically on the Acceleration activation component.

Also, you’re right that Microsoft doesn’t host MSXML 4.0 the way they used to. But I still would not try to “source” a loose msxml4.dll from anywhere. With MSXML4 you need a proper, registered install (and the activation error you posted is very commonly a registration/prereq issue, not just “missing DLL file”).

What I’d do next (in order)

1) Confirm whether MSXML4 is actually missing, or just not registering

1. Go to Windows “Apps” (Installed apps) and see if anything like “MSXML 4.0” / “MSXML 4.0 SP…” is listed.
2. Also check these folders for the file:
   C:\Windows\System32\msxml4.dll
C:\Windows\SysWOW64\msxml4.dll

If it’s in one/both places, you’re not “missing the DLL”, it’s more likely unregistered or broken.

2) If msxml4.dll exists, re-register it (safe check)
Open an elevated Command Prompt (Run as Administrator) and run:
regsvr32 C:\Windows\System32\msxml4.dll
regsvr32 C:\Windows\SysWOW64\msxml4.dll
You should get a “DllRegisterServer succeeded” message.

If you get “module not found”, “entry point not found”, or access denied, tell me the exact wording.

3) Re-run Acceleration’s activation trigger as admin
Even if you already “installed as admin”, the activation UI can be blocked by security/UAC at the moment it tries to launch.

1. Right-click the Acceleration setup.exe on the DVD and choose Run as administrator.
2. Temporarily turn OFF Windows Security “Controlled folder access” (if it’s enabled) just for this test, then run activation again.
3. Reboot once after any MSXML register attempt, then try the Acceleration start again.

4) Don’t worry about KB2758694 specifically yet
That “msxml4-KB2758694-enu.exe” file being absent from your DVD is not unusual depending on the disc run/printing. It’s a security update package, not the core runtime itself. The bigger question is simply: does your system have a working MSXML4 runtime registered.

A couple quick questions so I can point you to the cleanest “no sketchy DLLs” fix

• When you get the 0x800040005 error, where exactly does it show (Acceleration installer dialog, FSX splash screen, inside FSX when selecting Acceleration content, etc.)?
• After installing Acceleration, does FSX show “Microsoft Flight Simulator X: Acceleration” on the startup screen, or does it still look like plain FSX?
• Do you have “Controlled folder access” enabled right now (Windows Security -> Ransomware protection)?
• When you run the regsvr32 commands above, what exact message(s) do you get?

Once I know those four, I can tell you whether this is (a) a straightforward MSXML4 registration/prereq fix, or (b) the activation UI being blocked by Win11 security controls, which looks almost identical from the outside but needs a different approach.

Roy,

Understood — and thanks for being specific about where the 0x800040005 shows (FSX splash screen right when Acceleration should prompt for the key). That narrows it down a lot.

First thing: the “disc revision number” theory is a bit of a red herring. Those different part numbers were just different pressings/regions/bundles over the years. Some included extra prereq installers on the DVD, some didn’t. But Acceleration itself doesn’t “need” those EXEs to exist on the disc in order to activate — it needs the Windows components it relies on to already be present and working. On Windows 7/8/10 they often were (or were installed silently). On Windows 11 they often aren’t.

Also, if your Win11 box truly has no MSXML4 files in System32/SysWOW64, that’s totally believable — Win11 won’t ship it by default.

What I’d do next (keep it clean and methodical)

1) Confirm Acceleration actually installed (before we chase prereqs)

1. Start FSX.
2. Go to the top menu: Help -> About (or just look at the FSX splash text carefully).
3. Does it show “Acceleration” anywhere, or is it still plain FSX Deluxe?

If it’s still plain FSX, then we’re not even at the activation stage yet — we’re at a failed/partial Acceleration install.

2) Check whether Windows Security is blocking the activation UI
Even with “Run as Administrator”, Windows 11 can silently block the activation/registration bits.

1. Open Windows Security.
2. Look for anything about “Ransomware protection” / “Controlled folder access”.
3. If Controlled folder access is ON, turn it OFF temporarily.
4. Also check “Protection history” for entries around the exact time you launched FSX and got the 0x800040005.

If you see anything blocked/quarantined related to FSX/Acceleration, that’s a smoking gun.

3) Don’t try to source msxml4.dll — install/register MSXML4 properly
I know you said Microsoft no longer hosts it the way they used to, but the fix is still: you need a legit MSXML 4.0 installer (MSI) and then (if needed) registration.

Right now you’re in the classic state where Acceleration is installed but the activation UI component can’t spin up because a dependency isn’t there. A loose DLL dropped into a folder often won’t register correctly and tends to create a bigger mess (wrong version, wrong bitness, no COM registration).

4) After MSXML4 is installed, re-run Acceleration “repair”
Once the prereq is in place, don’t just keep launching FSX hoping the prompt appears.

1. Put the Acceleration DVD in.
2. Run setup.exe as Administrator.
3. If it offers Repair, run Repair.
4. Reboot.
5. Then launch FSX again and see if the activation prompt finally appears.

A couple of very targeted questions (so I don’t guess wrong)

1. When you say “None of the files… are on my Win 11 system”, did you check both of these exact paths?
   C:\Windows\System32\
C:\Windows\SysWOW64\
   (Win11 64-bit commonly uses SysWOW64 for 32-bit components like parts of FSX.)

2. Is your Windows 11 install 64-bit (almost certainly, but I want to confirm)?
3. What EXACT wording do you get with the 0x800040005 on the splash screen — is it “Product activation error” only, or does it mention an activation wizard failing to start?
4. Do you have any antivirus beyond Windows Security running?

Answer those, and I’ll steer you to the most reliable way to get MSXML4 installed on Win11 without random DLL downloads, and we’ll get your Acceleration key prompt back.

Roy,

That’s actually a useful clue: you do have “MSXML 4.0 SP2 Parser & SDK” installed (so the runtime isn’t totally absent), but FSX Acceleration’s activation is still failing at launch with the generic 0x80004005 “Unexpected error…” message. That usually points to one of two things:

1. MSXML4 is installed but not registering/accessible the way the Acceleration activation component expects (often 32-bit registration), or
2. something in Windows is blocking the activation/registration UI even though the install itself completed.

Let’s go at it in a clean, step-by-step way.

1) Verify the MSXML4 DLL is really present in Windows folders
Even if it shows in Apps, the real test is whether the DLL exists where Windows loads it from.

Please check these two exact paths and tell me which ones contain msxml4.dll:

C:\Windows\System32\msxml4.dll
C:\Windows\SysWOW64\msxml4.dll

(Yes, it’s counterintuitive: on 64-bit Windows, SysWOW64 is where 32-bit system DLLs live, and FSX/Acceleration is heavily 32-bit.)

2) Re-register MSXML4 properly (both 64-bit and 32-bit regsvr32)
On 64-bit Windows there are two regsvr32’s, and you want to hit the right one for each DLL.

Open Command Prompt as Administrator and run these exactly (some may fail if the matching DLL isn’t present — that’s ok, just report the message):

C:\Windows\System32\regsvr32 C:\Windows\System32\msxml4.dll
C:\Windows\SysWOW64\regsvr32 C:\Windows\SysWOW64\msxml4.dll

Then reboot once and try launching FSX again.

3) Check Windows Security “Protection history” (this catches silent blocks)
Even with “virus programs off”, Windows 11 can still block older activation/registration components without making it obvious.

1. Open Windows Security
2. Go to Protection history
3. Look for anything blocked/quarantined right around the time you launched FSX and got the activation error

If you see anything related to FSX/Acceleration/activation, post the entry details (what was blocked and the path).

4) Run an Acceleration Repair after MSXML4 registration
Once MSXML4 is confirmed/registered, don’t just keep launching FSX.

1. Insert Acceleration DVD
2. Right-click setup.exe -> Run as administrator
3. Choose Repair if it’s offered
4. Reboot
5. Launch FSX and see if the key prompt returns

A couple quick clarifiers (so I don’t steer you wrong)

1. When you said “In Program Files X64 I got File MSXML 4.0 …”, what is the exact full path to that MSXML folder/file you’re seeing? (Please paste it.)
2. Do you have FSX installed to C:\FSX\ (still), or did it end up under Program Files / Program Files (x86) on this Win11 machine?
3. When you run the two regsvr32 commands above, what exact messages do you get back for each one?

Once I know whether msxml4.dll exists in System32/SysWOW64 and what regsvr32 reports, we’ll know immediately if this is an MSXML4 registration/bitness issue or a Windows security block.