If you 'remove everything from my laptop and reinstall the os', then you lose everything ! If that is what you want to do, then restart with the OS X installer CD in the drive, while holding the 'C' key. Start the installer, and, at the screen where you select the drive for installing, choose your drive, and then click on the Options button, and choose to Erase the drive and install OS X. Follow the instructions to start the installation, and wait for it to finish.
If all you need is a password, then stop at the 'select a language' screen, click on the Installer menu at the top of the screen, and choose 'Reset Password'. You can then change the password for your administrator account. Quit the 'reset password' app, and then quit the installer. restart and login as the account with your new password.
And if you must reinstall anyway, then just do the reinstall without the password. You will make a new password during the user setup, then.