Forgotten your Windows password? Existing password won't work on your laptop or PC? Here's what to do when your Windows password won't work. (See also How to bypass Windows 8's password and Gain access to your PC without the logon password.)

QUESTION I own a Samsung laptop computer, which I've had for two years. I've always used the same password to start the computer, but now it's telling me that it's wrong, so I'm locked out of the PC. What do you suggest?

HELPROOM ANSWER There are a few things which could be happening here. First, make sure that you don't have Caps Lock or Num Lock enabled when typing your password – unless, of course, you had either in effect when you originally typed your password.

It's also possible there's a physical problem with your keyboard, so the password you are trying to type may not be what's actually being entered into Windows. Try booting up the laptop with an external keyboard plugged in to see whether you can type in your password on that keyboard.

From the age of your laptop, we're guessing that you have Windows 7 installed, but if you're running Windows 8 or Windows 8.1, you can click on the little 'eye' symbol that appears next to the row of dots as you're typing in your password as the sign in page. This will reveal your password, so you can verify that it's showing what you intended to type.

If you're signing in to Windows 8 or 8.1 with a Microsoft account – so you're using your email address and password to sign in – you can reset your Microsoft password online from a browser on another PC or from your phone. Click here and follow the instructions to reset your Microsoft account password. This will then apply everywhere you sign in with your Microsoft Account, for example Skype.

If you have a password reset disk, you can use it to reset your password and regain access to the laptop. However, you'll need to have created this yourself before you were locked out of the computer.

If there are any other users set up on the laptop who might have Administrator access, they can log in and reset your password for you from the User Accounts section of the control panel. Selecting the 'Manage another account' option and clicking on 'Change the password'. If none of these methods work, you can follow our instructions on resetting your password here: How to gain access to your Windows account if you lose your password.

Note that if you have protected any files using the built-in Windows encryption, you must NOT use the methods above to change your password via an administrator account as this will prevent you from accessing and files protected under the old password. The same goes for any stored passwords to network drives and websites.

In this case, you'll need to use a password cracking program to recover your original password. One such utility is Ophcrack. Use the bootable live CD option to create a disc you can boot and crack your existing Windows password. If you don't have a CD drive available, you can use a tool such as UNetbootin to create a bootable Ophcrack USB flash drive instead.

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