Another PowerShell command to note for future reference. Within my SharePoint farm there is often a need to migrate a user for one reason or another, e.g. their username may have changed. The Move-SPUser cmdlet migrates user access from one domain user account to another. If an entry for the new login name already exists, the entry is marked for deletion to make way for the migration.
Move-SPUser –Identity "DOMAIN\JaneDoe" –NewAlias "Domain\JaneSmith"