Your options to reset your password are outlined here:
http://ist.mit.edu/support/accounts/password
If you don't have an MIT certificate installed, AND if you can't visit us in person, the Accounts office can still reset your password if you follow these steps:
1) Email an image of your photo ID (usually taken with a smartphone) to accounts@mit.edu, or fax a copy of your photo ID to 617-258-6176. If you fax, please send on lightest copy possible since it gets darker when transmitted.
2) When you email or fax that photo ID, include a phone number you can be reached at.
3) When the Accounts team receives your photo ID and phone number, they will call you to facilitate a password reset over the phone.
This method, together with the methods described on the page linked to above, are the only ways to reset your Kerberos/Athena password.