Windows NLB and Apache

Hi all,
I have a question.
I want to deploy a solution based on Win 2003 Server with 2 servers in NLB.
On these server I'll use Apache and other Applications.

I would like to know if NLB is application oriented (EX: IIS/Media services,
ecc..) or is done at OS level.

For what I know should be done at OS level by Windows 2003, and there is no
need that an application "know" that is behind a NLB.

This is true?

I know that an application can be optimized to work in a NLB situation (EX:
Coldfusion) but is not strickly necessary. (Right?)

Thanks.

Regards