From TeamCity 8 you can log in as a super user and change the password that way. You just need to use an empty username and last occurrence of the “super user authentication token” found in the logs\teamcity-server.log file as your password.
Please see the following for more information:
- TeamCity 8 – http://confluence.jetbrains.com/display/TCD8/Super+User
- TeamCity 9 – http://confluence.jetbrains.com/display/TCD9/Super+User
- TeamCity 10 – https://confluence.jetbrains.com/display/TCD10/Super+User