For personal scans, you are better off using the scan to email functionality with the LDAP connection for the local addressbook. For scanning directly to the network it's more convenient to use a serviceaccount (account created in the AD meant for this service) with a set password.
If it's 'just' 2 or 3 pc's, you can setup the scanning option under 'services' and add two repositories. After you've added these repositories, you can simple select them from the scanning tab when creating a new template. You can set the passwords of these user accounts in the repository settings. Side-note; the passwords are send over the network unscrambled in so called 'simple' format. This if one of the reasons you normally use a service-account with no rights/mailbox.
Thank you for using the Support Forum. Please take a look at this solution for changing the password. This solution is from the support page for your machine and see if this will help. If not please consider contacting your support centre for further assistance.
We recently forced password changes to all our users for their Active Directory accounts. We have one office that uses the Scan to PC functionality quite heavily. However when they change their network password via the control panel to have the scan sent to their computer using the address book, the changes only work for that single scan. The next time they go to scan, they must again edit their password. I have not been able to find a way to edit this field either through the control panel or Web Interface to make it stick.