You see 0x8034001D and your network adapter goes dead. It's frustrating — a driver error that kills connectivity with no obvious cause. Let's fix it fast.
The Fix: Clear the NDIS Cached Mapping
Open Registry Editor as Administrator. Go to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e972-e325-11ce-bfc1-08002be10318}This is the network adapter class GUID. Inside, you'll see numbered subkeys like 0000, 0001, 0002 — each one represents a network adapter.
For each subkey, look for a value named Ndi\Params\NetworkAddress — skip that one. What you're after is any value named MapSubDir or MapFileName.
Delete every MapSubDir and MapFileName you find. Don't touch other values. Then reboot.
Why This Works
The NDIS (Network Driver Interface Specification) layer maps driver files into kernel memory. When Windows caches those mappings — because it's trying to be smart about reusing them — and something changes (driver update, adapter swap, power state transition), the cache still points to the old mapping. Your new driver load attempt hits that stale mapping and gets ERROR_NDIS_ALREADY_MAPPED.
What's actually happening here is: the MapSubDir and MapFileName entries store the file path and subdirectory of the driver's mapped region. They're cached for performance. But when they go stale, Windows sees the file as already mapped and refuses to re-map it — even though the old mapping is invalid. Deleting those entries forces NDIS to rebuild the mapping from scratch on the next boot.
The reason step 3 works is: it removes the exact cache entries that trigger the conflict, without touching the actual driver files. No reinstalls, no driver rollbacks.
When the Standard Fix Doesn't Cut It
If that doesn't help, you've got a deeper cache issue. Open an elevated Command Prompt and run:
netcfg -dThis resets all network adapters and their bindings. This will wipe your network profiles — VPN connections, static IPs, Wi-Fi passwords — gone. So back up any settings you care about first.
Alternatively, the error can come from third-party NDIS drivers — like virtual adapter software (VMware, VirtualBox, Cisco AnyConnect). Those install their own NDIS miniport drivers. If the error appeared after installing one of those, uninstall the software completely, reboot, then reinstall the latest version.
I've also seen this on Windows 10 20H2 through 22H2 after a Windows Update that replaced the ndis.sys file without properly flushing the mapping cache. In that case, a sfc /scannow followed by dism /online /cleanup-image /restorehealth can fix the system file, but you'll still need to clear the registry cache afterward.
Prevention
Don't install multiple network virtualization tools on the same machine. Each one registers its own NDIS miniport driver, and their mapping caches can collide. If you need multiple, use them sequentially — install, use, uninstall, then install the next one.
Also, avoid manually assigning static MAC addresses through the adapter's advanced settings unless you absolutely have to. That creates a NetworkAddress parameter that can sometimes interact badly with the NDIS mapping cache — especially if you toggle power management on the adapter.
Finally, keep your network driver directly from the chipset vendor (Intel, Realtek, Broadcom), not from Windows Update. OEM drivers from the manufacturer tend to update the NDIS mapping table correctly. Windows Update's generic driver sometimes skips that step.