What to do if you land in a situation when you have lost your administrator account password and cant get in XP system?
Some of the ways that I know to get in are mentioned here . These steps should be tried only when you have no other way of getting in, as wrong procedures can probably get you in more trouble.Dont try these steps on a system that is not yours.If you have created a password reset disk, than use that.
1) What to do: At the logon screen press ctrl+alt+del twice, a dialog box will appear .Type in username as"administrator" and leave the password blank and enter. You will get in if the admin password is set to blank. If you succeed, go to run and type "control userpasswords2".In the new window you can edit or delete any account or passwords.
How does it work: When XP is first installed ,during the setup, the user is asked to provide an administrator password which is for an admin account that is automatically created.Most users skip this thinking that they will later create a new admin account from control panel and put a password there.So this default account remains with a blank password .You will never use this account to log on in normal run , it is only for emergency purposes .Most of the OEM versions that come factory installed have this password as blank (which is obvious as they cant put a different password for everyone and convey it to them) or some may have a default other than blank.This administrator account is not visible during normal logon and can be activated by above procedure.
How to protect your system against this: Very simple.Put a password there when you install XP , or if you haven't done that, get into this admin with blank password and change it. Never log in with this admin for normal purposes.This thing wont work with vista.
2) What to do: A bit risky, so do it at your own risk. Insert the XP installation CD and boot from it, instead of new setup go for repair the old installation. Normal repair procedure will begin and a restart will occur.Now look carefully at the captions. When it says "installing devices", hit "shift+F10".In the window that appears type in "nusrmgr.cpl".You can easily edit any user accounts in the window that appears next.
How to protect your system against this: What i have done on my system is that first change the boot sequence to HDD first rather than CD/DVD and assign a supervisor password in BIOS.So no one can boot from any other place other than HDD without BIOS supervisor password. Remember that this supervisor password is different from user password in BIOS. You have to key in the user password every time you boot (a bit annoying), but the supervisor password is needed only when you edit your BIOS options(and not on every boot).This also wont work with vista as its a sort of security hole in XP (haven't tried this on SP3 yet).
If above fails then there are some 3rd party tools to boot with and get the passwords but i haven't used any (i don't trust any), so i wont write about them.But changing the boot menu will protect your system from such an attempt.
The last option you have is to only do a reinstall .Don't format the other partitions and your data will be safe. Always make aa separate partition for your OS which you can format easily without disturbing other data.
open regedit.exe from run.go to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion|Internet Settings .Here create a new DWORD value named "DisablePasswordCaching" and set it to 1.
2)Disable the default administrator account : Although its better to put a password there , you can disable it.
open run and type "lusrmgr.msc".Here you can disable the default administrator account.
3) Make it compulsory to press ctrl+alt+del before logon: This will prevent you from automated bot attacks as this will make it mandatory to press ctrl+alt+del before you enter your username and password.
go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\Winlogon . Create a new DWORD value named "DisableCAD" and set its value to 0.
4)Make strong passwords: make them long, mix in alphabets both in small and capitals with numbers.
PS: plz make a backup of your registry before editing it.Dont try to get into someone else security, it will only get you into trouble.
This is my first doc here, so any suggestions will be appreciated which would help me to do better in future. I will add new things especially for vista users when i have tried them.