Everyone is given a default password when they register to use the computers.
Some people are quite happy to keep it whereas others wish to change it to something more memorable.
The following describes how to do this. The easiest way for the majority of users is to use the icon provided on the NT workstations. The change may appear instantaneously on some machines but on other may take a while to propogate throughout the system so be patient. Common combinations of letters forming words etc. These are all equivalent.