how to specify different Java to NetBeans

Hi all,
i've downloaded NetBeans for the first time and it has been the first time i'm trying to use/learn any Java IDE.
i had a question. NetBeans seems to identify the Java on its own when we install but what if i want to change that java? how can i do it?
e.g. if NetBeans uses jdk1.4 and i wanted to make it work on 1.3.1 or vice versa (of course the Swing compatible java will have to be used in anycase)...
u might wonder "wow! this guy has never used IDE?"...yeah..i never got a chance to use IDEs..i work on vi platform a lot and find no time to learn IDE as always find myself in neighbourhood of deadlines u know

i'm good in vi, command prompt execution etc...but wanted to know the power of IDEs as i heard from all the ppl...
please help me.
regards
maulin.