No need to use the paid tools suggested by @llamaths. If you search on google, you’ll find many Windows password recovery & reset methods and freewares:
http://pcsupport.about.com/od/toolsofthetrade/tp/passrecovery.htm
http://www.top-password.com/knowledge/reset-windows-password-without-cd-usb.html
You can also get lots of video tutorials on youtube. If you still couldn’t reset your password on your own, you might need to take your computer to a repair shop.
