You can log on as administrator on safe mode. Press F8 when you start the computer and choose Safe Mode to get in. If you can not log in safe mode, try the tool bellow, it is the best method without lose anything.

In consideration of remaining all programs and data of the computer, I recommend you to use a password tool: Windows Password Recovery Tool 3.0. It supports all versions of Windows operation system. Recover Windows password without lose anything. Here are the simple guide:
Step 1: Download Windows Password Recovery Tool 3.0 and install it in any available computer
Step 2: Burn a bootable CD/DVD or USB flash drive
Step 3: BIOS settings of your locked computer to make it boot from CD/DVD or USB flash drive
Step 4: Reset Windows password successfully