There is a difference between the academic and normal retail version of software, but it's not in the code, oh no. The licences for the two products are different. If I recall correctly (most likely not) the licence for the academic version prohibits using it to make money i.e. you can not release any game you produce with it for cash. I don't know how Microsoft can tell, or even if they bother checking though (can't see that they would as it would be quite anal, but...).
If we are talking pirated software I may as well throw in my tuppence worth:
I have no moral objection to people using pirated software to see what it is like, but if they like it and decide to keep it then you've got to cough up. Like a self regulated form of Shareware. Of course it depends on everybody else thinking the same way (which they don't)
[This message has been edited by STG (edited November 25, 1999).]