Windows XP, both Professional and Home Edition, use the Welcome screen to support Fast User Switching.

NOTE: Windows XP Professional in a domain environment automatically reverts to the classic logon screen. You can enable the classic logon screen, using tip 4485 ยป How do I configure Windows XP to use the classic logon screen?

While assisting a neighbor, I learned that the Administrator account is only available on the Welcome screen of Windows XP Home Edition in Safe mode.

While configuring an alternate install, I discovered that the Administrator account is only available on the Windows XP Professional Welcome screen if no other account is a member of the Administrators group.

NOTE: This behavior only became apparent after a restart.