You don't state the OS but usually it is a damaged system file.
On XP you can try this: Boot computer and press Ctrl+Alt+Delete twice when you See Windows welcome screen / login screen. It`ll show classic login box. Now type "Administrator" (without quotes) in username field and leave password field blank, press Enter and you should be able to login Windows. Now you can reset your account password from "Control Panel -> User Accounts". On Win 7 or Vista: Ctrl+Alt+Delete won`t work, you have to use some windows password recovery software. I recommend Windows Password Reset Deluxe
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How to reset wespro n720 mini laptop My wespro n720 is start but hang all...