http://windows.microsoft.com/en-US/windows7/Remove-stored-passwords-certificates-and-other-credentials
Remove stored passwords, certificates, and other credentials
If you no longer need credentials stored on your computer that you use to log on to websites or other computers on a network, follow the steps below to delete them. For more information about stored credentials, see Store passwords, certificates, and other credentials for automatic logon.
Open User Accounts by clicking the Start button
, clicking Control Panel, clicking User Accounts and Family Safety (or clicking User Accounts, if you are connected to a network domain), and then clicking User Accounts.In the left pane, click Manage your credentials.
Click the vault that contains the credential that you want to remove.
Click the credential that you want to remove, and then click Remove from vault.
