need to Change computer name

hi

i have windows 2000 server domain,
and i have mixed clients win98, NT workstation, 2000 proff

i want to change the computer name of all the client machines
how can i do that, can i simply put some other name,
will it affect any thing in functioning of the pcs
and what all then steps to be taken care while doing this
pls specifiy OS wise

Thanks