what are requirements for sql server 2005 installation?
how to connect it with netbeans>
can we make no. of instances?how and why?

requirements for sql server 2005, check their website, there should be a nice overview of them.
you don't connect it to an IDE, you just create a connection in your code. you may want to check out jdbc.
what do you mean with: make no. of instances?

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