Trick to change the admn password in win7 without knowing the current one...

1. Go to control panel and double click on administrative tools.

2. one window will open in that window double click on computer management. 

3.you will see there are three options i n that double click on system tools 

4. Now double click on Local Users and Groups. 

5. now double click on Users. 

6.well you will see there are 3 users admin , guest and standard. (I have hide my name) 

7.now Right click on Administrator you will see 1st option set password…. :D now just select that option.

8. Now click on proceed and you will see this window.(as shown in bellow figure)