Hello, this is Emily.
If you hold down Windows + R keys, type in netplwiz and press enter. how many account do u see there? If you still see the old account, yo can delete it here.
Type sysdm.cpl in the search on the taskbar and hit enter, go to Advanced tab, click on the "Settings" button at the User Profile section. Then delete the old user profile.
Let me know if that addresses the issue. If not, I need a bit more information regarding where you are still seeing the reference of the old account, so I can answer further. Thanks!