XP net user create account, change password, never expire

In Windows above Vista you need to open cmd with administrative priviledges: menu/cmd/right-click/open as admin

Create a user with a password and options:

net user username password /ADD /PASSWORDCHG:NO /EXPIRES:NEVER

Once created you can assign that user to a group:

net localgroup administrators username /ADD

Change a password:
net user username password

Change expires option:

net user username /EXPIRES:NEVER