You could download OPHCRACK for Windows which is free password recovery tool. You must download the correct version for your computer ie. Windows VISTA and Windows 7 or for Windows XP. Once you have downloaded the correct one you have to burn it to a disc to use it. Now go to your bios and change your bios to boot from your dvd drive and with the disc inserted boot your computer and the program should find all of the Windows passwords on your computer and then write them down and the chose the correct one to use. Don't forget to change your Bios back to boot from your hard drive after you have finished.