Do you mean you want to unlock Windows password? If so, you can try your password hints and password reset disk firstly if any. Besides, it is recommended to reset with some password recovery tools. It is not suggested to re-install your system, for it will cause data loss.

You can reset a lost or forgot Windows password with 4 methods below:

1. Another valid administrator account which can normally log on.

2. A password reset disk or a repair disc, which is created in advance ( before you lost password ).

3. Third-party software to create a bootable password reset CD/DVD or USB, like Windows Password Breaker.

4. Re-install. Will lose data.