3ds max 7 and auto desk /autocad software

[Devastater]

hey, im a new to modeling and animating and have been messing with the 30 day trial off of max's website but i just recently found out that we got software packages with max 7 and auto cad and the whole "auto " family, but i noticed when i opened the box that there is a serial number but no cd key, does that mean that i only have that for 30 days? or do i even have to put a cd key in or what?? i don't want to try installing unistalling on my school comp because it was hard enough as it is to get the trial on there with pewrmission etc and i want to know all the details of the liscence authorization etc.......thanks in advance for help Please respond!