Change the account username in Windows 10 when signed in with a Microsoft Account
Method 1: Change the account name in Control Panel.
1. Access Access Control Panel / User Accounts and Family Safety / User Accounts.
2. Select “Change your account name”.
3. Enter a new name in the box and click Change Name.
Method 2: Change the account name in Local User and Groups.
Step 1: Open Run Windows + R, type lusrmgr.msc, and click OK to open Local Users and Groups.
2. Open the Users folder, right-click on the user, and select Rename in the menu.
3. Enter a new name in the name box.
Method 3: Change the administrator or guest name in the Local Group Policy Editor.
1. Access Local Group Policy Editor.
2. Open Computer Configuration / Windows Settings / Security Settings / Local Policies / Security Options / Accounts: Rename administrator account: Rename the admin account (or Account: Rename the guest account).
3. Enter a new name and press OK.