how to break a login user password without any backup disk?

Step 1
Restart the computer.
Step 2
Press and hold down the "F8" key as the computer is booting. Release "F8" when a list of options appears and select "Safe Mode With Networking" from the list.
Step 3
Click on the "Administrator" account.
Step 4
Press the Start button on the lower left-hand side of the screen.
Step 5
Type "control userpasswords2" in the text field that appears and press "Enter." Uncheck "Users must enter a username and password" and restart the computer. It will be unlocked.
Step 6
If this does not resolve the situation, press the Start button and chose Control Panel from the menu that appears. Click the arrow in the Control Panel to bring down a drop-down box and choose "All Control Panel Items." Navigate to "User Accounts" and then "Manage Another Account." Choose your account and select the option to edit it. Select "Remove the password." Repeat for every account accessible through the Control Panel.