1.Use the built-in administrator account which you can logon without password in safe mode.It was built when you install your system and its password default as blank.
Press ctrl+alt+delete twice in the welcome screen and you can see a classical logon dialog box,type administrator and press Enter.Or you can press F8 when you start/restart your computer to select start from safe mode.

2.Use a password reset disk If you have created ever.Of course it must be created for your current password.You can find a prompt when you input a false password in the welcome screen.Clik it and follow the guide:how to create Windows password reset disk.

3.If the two methods above cannot help you,you can find a recovery tool.As far as I know, there are many password tools on the network, but I have used is "Windows password rescuer personal/professional/advanced " ,it is simple and safe that the average person will use it. It can soon reset the password in several minutes.Only four steps can help you reset the lost Windows password:

Step 1: Download Windows Password Rescuer and install it to another computer.

Windows Password Rescuer Professional free download.

Step 2: Run it and burn it to a bootable CD/DVD or USB flash drive.Before this confirm that you have insert a blank bootable CD/DVD or USB.



Step 3: BIOS setting:Setup your own computer boot from CD or USB.Press F2 or DELETE when you start/restart your PC to get into the BIOS SETUP list.



Use arrow keys to select boot manu,and use +/- key to move the CD/DVD or USB option to the first site.



Then inset the CD/DVD or USB you have just created for recovering password. Press F10 to save and exit.



Step 4: Reset Windows password: Wait for a moment,it will display friendly operate window,and you can reset whichever password on it.



More details: Recover Windows 2000/XP/VISTA/WIN7 password with Windows Password Rescuer Personal/Professional/Advanced