On Windows 7 machine, open credential manager and remove the credentials you would like to clear that contains Network share authentication information.

1.       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.

2.       In the left pane, click Manage your credentials.

3.       Click on the credential you would like to remove, and then click on Remove from vault.

From Command line:

Start > Run > cmd

and type:   net use * /DELETE