In case of user password boot the pc in safemode by pressing the F8 key and then selecting the Safe Mode option।
You can now logon as an administrator and XP wont prompt for the password.
Incase of an administrator account try rebooting the pc in DOS. access
C:\Windows\system32 \config\sam . Rename SAM as SAM.mj
Now XP wont ask for password next time You Login. Also
Go to the cmd prompt .
Type net user *.
It will list all the users.
Again type net user "administrator" or the name of the administrator "name" *.
e.g.: net user aaaaaa *(where aaaaaa is the name).
It will ask for the password.
Type the password and there you are done.
Logging In As Administrator:
Hold the Ctrl-Alt key and press Del twice. This will bring up the normal login and you can log on as Administrator.
How to Log on to Windows XP if You Forget Your Password
Here is a simple way to access Windows XP with Administrator rights and privileges if you have password protected your User account on your Windows XP system and can't remember the password(s) to login। Whenever Windows XP is installed on a system, it creates a default account called "Administrator" and by default this account is not password protected. Therefore, if you bought a brand name computer (such as Dell, HP, Compaq or Sony) — or installed Windows XP yourself — you should be able to login to the computer through the unprotected Administrator account.
StepsReboot your machine।
Press F8 before the Windows Boot screen appears।
Do not press F5 as used on the NT/9x series of Windows।
You will be be prompted with a boot options menu।
Select the Boot Windows in Safe Mode option।
Click through several self-explanatory screens until your reach the familiar 'Welcome' screen।
Note that this welcome screen is limited to 256 colors and 640x480 resolution because the primary graphics will have been set to the Windows Safe Mode software VGA adapter। You will not be able to change this mode even in Display options, while Windows is running in Safe Mode.
Find the icon for the Administrator user। If the default settings of your system haven't been changed, there should be no password for this account.
The Safe Mode Welcome screen might display some of the other users on your system।
Login as the admin।
Press Yes at the prompt asking if you would like to continue using Safe Mode।
Continue on to the User Settings control panel। Here you can change any of the other passwords for user on the machine. Make any changes you want.
Reboot your computer। As long as you don't press any keys (i।e. F8) during the boot-up the computer will startup normally. Login as the user for which you set the password.
Modified By Prem
for more details
To unhide the Administrator account so it does show up:
Start Regedit (Ctrl+R)
Go to HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows NT \ CurrentVersion \ Winlogon \ SpecialAccounts \ UserList
Unhide the Administrator key by giving it a value of 1