Solution 1 : Using the Administrator Account
1- Start or restart your computer and press "F8" while the computer boots up. The Advanced Boot Options screen appears.
2- Scroll down to "Safe Mode" with the arrow keys on the keyboard and press "Enter." Your computer starts in Safe Mode.
3-Click on the "Administrator" account that appears on the Windows logon screen
4-Click on "Start" and "Control Panel".
5-You will enter "All Control Panel Items", then click" User Accounts"
6-Then click"Manage Another account" as following.
7-Choose the account which you want to reset the password.
8-Click "Change the password" as following
9-Type a new password ***** that account.
If you don't see the Administrator account then you will need to create one :
restart your computer and press "F8" Scroll down to "Safe Mode with command prompt", a black box will appear, please type :
net user Administrator /active:yes (and click enter)
now restart your computer and follow the previous steps.