How to Reset a Windows Vista Password Without the Repair CD
You can set up Microsoft Windows Vista with multiple user accounts, each with its own password. Vista provides the option to create a password reset CD that you can then use to reset forgotten passwords. If you don't have a password reset CD available, you can still reset the passwords through your Vista administrator account.
Log into Windows Vista under the administrator account.
Click the "Start" button.
Type "lusrmgr.msc" into the Search field. Press the "Enter" key.
Enter the administrator password to confirm that you wish to open this file.
Double-click the "Local Users and Groups" icon. Select the "Users" tab.
Right-click on the user account that needs its password reset. Click the "Set Password" option from the drop-down menu.
Type the new password in the two fields that are provided. Click "OK" to accept the change.