If you are a non-administrative user please contact the system administrator to reset your password.
If your are the administrative user you can reset your password from the command line with
sawmill -a rra -u username -pw password
This command will reset your root admin username and password.
On Windows you can run this command from the command prompt by typing e.g.
c:\
cd c:\Program Files\Sawmill 8
Sawmill -a rra -u "my username" -pw "my password"