An Administrator can choose expire passwords for all users any time they want to enforce extra security for their organization.
Tips on Expiring Passwords
Consider the following when expiring passwords:
- After you expire passwords, users might need to activate their computers to successfully log in to Salesforce.
- (See Activating Your Computer.)
- For more options you can set to ensure password security, see Force.com's Setting Password Policies.
Navigate to Setup

Click on Your Name
Select Setup

Under Administration Setup
Choose Security Controls
Select Expire All Passwords

Select Expire all user passwords and then click Save to expire the passwords for all of the users in your organization. The next time the users log in, they will be asked to set their passwords to a new value.