1. To Start This Trick,You must have an admin access to system whose password you are going to change.
2. Now Click On Start, Type "cmd" In Search Box,Right Click On CMD (1st From Result) And Click On "Run As Admin".(For Windows 7 Only, XP Users Can Click Directly On CMD From Search Result).It Opens Command Prompt Window!
4. Type " net user YOUR_USERNAME * "(Without Quotes) .Here YOUR_USERNAME is Username Of That Account Whose Password You Are Going To Change (Username Is Case Sensitive)!
It's Very Useful To Fool Your Friends,When You Have An Access To His/Her PC ,Laptop With Admin Privilege And If You Want To Fool Him/Her By Changing His Default password Then You Can Simply Use This Trick,Whether You Don't Even Know Single Character Of His/Her Password!