AFAIK, if you don't disable an account using Local Users and Groups snap-in, it will keep appearing on the login screen.
For specifically hiding an account from login screen, use registry:
- Go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon.
- Create SpecialAccounts sub-key to Winlogon. Then create UserList sub-key to SpecialAccounts.
- So at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList, at the right pane create DWORD value with name of user account name you want to hide.
- Set the DWORD value data to 0.
Restart your system to make changes effective.
PS. Create a System Restore point before making any changes to registry.