Method1: if you want to change your windows 7 password with-out opening User Account on Control panel then you follow the following steps.
Step1: first you open cmd (Command prompt) in the following...
1) Go to C:/windows/system32.
2) Copy cmd.exe and paste it on desktop.
3) Rename cmd.exe to sethc.exe.
4) Copy the new sethc.exe to system 32, when windows asks for overwriting the file, then click yes.
5) Now Log out...