How to change the User Login in Win XP

If you wants the classic way of login: Press Ctrl+Alt+Del to login
In the control panel, click on "User Account" on this control, under "Pick Task"
select "Change the way users log on and off". On this window uncheck "use welcome screen" and "Use fast user switching". This will revert you back to the traditional WinNT/Win2000 style of logging in.
OR

Start -> Run -> Regedit and change the following value:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\Winlogon look for "LogonType" in there and change the DWORD value from 1 to 0 (double click on it and enter 0 in popup the)...after a restart you should have the classic logon-box...

If you don’t want the classic way of login: Reverse the steps:

Start>>Control Panel >>User Accounts >>Select Change the way users log on and log off>>Check the option>>Use Welcome screen & Use Fast user switchingThen restart the computer.You will not get the traditional style of logging in.
OR

Start>Run>>Regedit>>HKEY_LOCAL_MACHINE>>Software>>Microsoft
>>WindowsNT>>CurrentVersion>>Winlogon and look for “LogonType” in their change the DWORD value from 0 to 1.Then restart the computer.