i had the same problem before. What I did is run my system in safe model and login as the default administrator( The Super Administrator Account). and change my administrator password '
Here's some step . I hope can help you.
1) Restart your pc and press F8 after hardware check and before your operatimg system loaded. ( when pc starts to run there the first scren you will see is a scren includes productor symbol like DELL and your processor's symbol. In some other motherbord bassed pc it may looks more like a DOS scren; Press F8 after it and before you see the system symbol like Windows XP. But if there are more than one operating systems installed on your pc. that is much easier, just press F8 when you see the run menu)
2) After that step you will see a menu that ask you which model do you want to run as. Choice "Safe Model" (Normally that is on the top of scren) and press Enter.
3) if there is only one operating system installed on your pc, then please straight go to step 4. Choice which OS do you want to run under safe model and press Enter.
4) When the OS loaded you will see more than one administrator accounts on your pc. One is that which you forget its password and one is the default account which you cannot see normally and has no password. Log into it and change your account's password in "Control Panel"\ " All Users"\ your account\ "Change Password" or " Disable Password"
NOTE this willl delete some of your current password file. please back it before you do it.
I hope this will help you.
Good Luck!