Turn off Settings → Bluetooth & devices → Printers & scanners → Let Windows manage my default printer, then set your default. If it still fails, restart the Print Spooler and remove stale printers.

What 0x00000709 means

0x00000709 maps to ERROR_INVALID_PRINTER_NAME: Windows couldn't save the new default printer, generally because the user's registry key for it is locked (missing permissions) or holds a stale printer entry. Separately, 'Let Windows manage my default printer' greys out manual changes, so turn it off first.

What you'll see

  • “Operation could not be completed (error 0x00000709)”.
  • Default printer keeps changing back.

What causes 0x00000709

  • Windows managing the default printer.
  • Stale printer entries or registry permissions.
  • Hung spooler.

How to fix it

  1. Turn off automatic managementUntick Let Windows manage my default printer, then choose Set as default on your printer.
  2. Restart the spoolerRun net stop spooler and net start spooler as admin.
  3. Remove old printersDelete printers you no longer use in Printers & scanners.
  4. Registry (advanced)In regedit, go to HKCU\Software\Microsoft\Windows NT\CurrentVersion\Windows, right-click the Windows key → Permissions and give your account Full Control, then set the default printer normally in Settings. If you edit Device by hand, it must use the format Printer name,winspool,Port: (for example HP LaserJet,winspool,Ne01:). Back up the key first.
Check it's fixed: Your chosen printer shows 'Default' and stays selected after a restart.

Stop it happening again

Keep automatic default printer management off if you use several printers.