Fix 0XC0261006 Monitor Invalid Serial Number Error

Your monitor's EDID serial number is missing, duplicated, or corrupt, so Windows refuses to load the saved display config. The fix is usually a clean EDID re-read, a driver reset, or editing the registry block directly.

Quick answer: Windows is rejecting your saved display config because the monitor reports a missing, blank, or duplicated EDID serial number. Reset the display driver, force an EDID re-read, and if that fails, edit the MONDSC block in the registry.

You'll run into this one most often after plugging a cheap DisplayPort KVM, a passive HDMI splitter, or a second identical monitor into the same machine. Two identical panels with the same serial number confuses Windows — it can't tell which config belongs to which display, so it falls back to a generic one and throws 0XC0261006 at you. You might see it as a black screen on the second monitor, a stuck "Preserve display settings" prompt, or a system tray warning that a display isn't working. On OEM machines (Dell OptiPlex, HP EliteDesk, Lenovo ThinkCentre) it can also pop during a dock switch, because the dock firmware sometimes strips EDID bytes on the handshake.

The core problem: Windows stores a per-monitor config block under the MONDSC registry key. If the monitor's serial number fails validation — blank whitespace, all zeroes, an obviously fake value like "0000000000", or a duplicate already present — Windows won't apply the block. The fix is to nudge the handshake and, if needed, clear the corrupt block so it rebuilds cleanly.

Step-by-step fix

Unplug everything but the problem monitor. Yes, really. Disconnect the KVM, splitter, or second display. Boot directly into Windows with one cable straight from the GPU to the monitor. This removes the most common cause — the duplicate-serial collision — before you even touch software.
Reseat the cable at both ends. DisplayPort and HDMI handshakes drop EDID bytes if a pin doesn't make solid contact. Swap the cable if you have a spare. Cheap cables that worked yesterday occasionally stop negotiating EDID properly after a bend or a tug. After reseating, wait 15 seconds. You should see the monitor flash and Windows re-detect it in Settings > System > Display.
Restart the graphics driver with a keystroke. Press Win+Ctrl+Shift+B. The screen goes black for a second, then beeps and comes back. This forces Windows to re-enumerate the display pipeline without a full reboot. If the error appears in an event log or tray notification, check whether it stopped reappearing.
Reset the display config in Settings. Open Settings > System > Display > Advanced display. If you see a "Reset" button or an option to forget a saved arrangement, use it. On Windows 11 22H2 and later, the option is under Advanced display > Display information. After resetting, sign out and back in — not just a restart. The per-user display config rebuilds on sign-in.
Update or roll back the GPU driver. If you just updated to an NVIDIA Game Ready driver (say 551.86 or later) or an AMD Adrenalin 24.x release, that's a suspect. Use DDU (Display Driver Uninstaller) in safe mode to remove the driver fully, then install the previous known-good version. For Intel Arc and Iris Xe, driver 31.0.101.5333 fixed a string of EDID bugs — grab it if you're on anything older.
Clear the corrupt MONDSC block in the registry. Only do this if steps 1–5 didn't stick. Back up first: File > Export in regedit, save to your desktop.
```
regedit.exe
```
Go to this path:
```
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\GraphicsDrivers\Configuration
```
Inside, you'll see subkeys with long GUID-style names — each one is a saved display configuration. Right-click each and check for a SetId value that references MONDSC. When you find the one tied to your problem monitor, delete the whole key. Close regedit, reboot, and Windows will build a fresh config with the current EDID serial number.
Confirm the fix. After reboot, open Event Viewer > Windows Logs > System and filter for the code 0XC0261006. You should see the last entries stop at the reboot timestamp. Set your display arrangement the way you want, restart once more, and confirm it sticks.

If that didn't work

Force a fresh EDID pull. Boot into safe mode with the monitor connected, then reboot normally. Safe mode loads Microsoft Basic Display Driver, which re-reads EDID without any vendor overlay. This clears stale cached values that the normal driver path won't touch.
Try a different port. Move from the GPU's DisplayPort to HDMI, or vice versa. On some Lenovo and Dell docks, only one port negotiates EDID cleanly — the others silently drop the serial field.
Check the monitor's own EDID. Monitors from no-name brands sometimes ship with all-zero serial numbers. You can dump the EDID with Monitor Asset Manager and look at bytes 12–15 of the descriptor. If the serial is blank, that's a hardware-level problem — RMA the monitor or set an EDID override.
Install an EDID override. A tool like CRU (Custom Resolution Utility) lets you write a synthetic EDID with a valid serial number. This is a last resort, and it can brick the display config if you get it wrong. Back up the existing EDID first.

Prevention

Don't chain passive splitters or cheap KVMs between your GPU and your monitor if you care about display settings sticking. Active DP 1.4 KVMs ($the ones with their own power supply$) preserve EDID properly; the $20 passive ones don't, and you'll fight this error every time you switch inputs. Also avoid running two physically identical monitors on the same output — even when serials differ, some panels report the same fallback value. If you must, put one on DisplayPort and the other on HDMI or USB-C so Windows tracks them as separate device classes. And when you update GPU drivers, keep the previous version's installer around. Rolling back is ten minutes; chasing 0XC0261006 through the registry is an evening.