-Go to control panel
-Select “User Accounts and Family Safety”
-Select “User Accounts” option
-You will see at the top portion “Make changes to your user account”, select “Remove your Password”
-Now you will need to put a current password. Then select remove password to confirm. The close the user account window...

Or use the Advanced User Accounts Control Panel.

- Click the start button then type “Control Userpasswords2″ in the Start Search box.
- To configure the automatic log on, select your user name in the Users For This Computer list, if it isn’t already selected. Then clear the Users Must Enter A User Name And Password To Use This Computer check box.
- you’ll see the Automatically Log On dialog box,then you will need to type your password in both the Password and Confirm Password text boxes. To complete the operation, click OK.

hope this helps.