Windows 7 forgot how the changed password landed?

In most cases, if you forget your password and you do not create a password reset disk and have no other administrator account that you can use to log on, there is no way to log on to the Administrator account without reinstalling Windows.
However, if you still remember your old password, you can try to use the system to log on.
Note: To use this method, the computer's restore point must be a successful logon time.
1. Insert the Windows 7 DVD, and then restart the computer.
2. After receiving the following message, press any key:
Press any key to start from CD or DVD
3. Set the following preferences, and then click Next:
 Languages to install
Time and currency format
 Keyboard or Input method
4. Click Repair Computer, select the operating system that you want to repair, and then click Next.
5. Click System Restore, and then click Next.
6. Click the restore point that you want to use, and then click Next.

Note: Click the restore point where you can restore your computer to a successful logon state. After you use the System Restore feature, reinstall all programs and updates that may have been removed. No personal documents will be lost. However, you may need to reinstall the program. You may also need to reset some personal settings.
7. Confirm the disk you want to restore, and then click Next.
8. Click Finish, and then click Yes when prompted.
9. After the System Restore process completes, click Restart to restart the computer.
10. After the computer restarts, click Close to confirm that the System Restore process has completed successfully.
11. Log in using the appropriate method. For example, log on with an old password or log on with another computer account.