Moral/legal question

I use ACAD 2004 at work.

I would like to now purchase a copy for home for off-hours consultancy
work. My system is a W98 system that works fine and for reasons not
relevant enough to go into here, I do not want to upgrade it to WinXP
at present.

Can I purchase a copy of ACAD 2004 and install instead a pirated copy
of Acad 2002? I have tried obtaining a copy of 2002 but all the
AutoDesk distributors in my country say it is not available. My copy
of 2004 would then just sit on the shelf and would not be used on ANY
computer. What is the legal or moral position of what I am proposing?

All viewpoints welcomed.