Step 1. Get a Linux Live Cd
Step 2. Boot the cd
Step 3. Go to C drive>Windows> System 32 folder
Step 4. Rename "Utilman.exe" file to "Utilman1.exe"
Step 5. Now rename "cmd.exe" file to "Utilman.exe"
Step 6. Restart your PC and remove the cd properly
Step 7. Hence you will get an screen of user login afterwards.
Step 8. Now click on "Ease of access"(left bottom corner of the screen) and cmd.exe will pop up.
Step 9. Type "net user",without quotes in command prompt it will show all users list
Step 10. Now you have to add a new user so type
net user DunyaInfocom pass /add
here your new username is "DunyaInfocom " and its password is "pass"
Step 11. Now you have to make this user as a administrator ,so type
net localgroup administrators DunyaInfocom /add
Step 12. Restart your pc, and login with your new user here its "DunyaInfocom" , give the password "kow".
Step 13. Now its done ,now you may delete your old user account or change its password from control panel
Step 14. But that's not end, your PC is to totally correct , to make it correct again boot with your Linux cd and go to C drive>Windows> System 32 folder , now rename "Utilman.exe" to "cmd.exe" and now rename "Utilman1.exe" to "Utilman.exe".
For Change Password of existing users
net user username password