Cluster questions

First of all, excuse me if my English isn't too correct.

I need to install a portal infrastructure that was developed with ASP
and SQL Server. The system would like to be redundant and scalable.

To do that, I have in mind, the following diagram :

- 2 W2003 Servers with IIS6 and NLB ( frontend )
- 2 W2003 Servers with MS-SQL and MSCS with a SAN connected ( backend

I have read Microsoft and others documentation, and I have questions
that I would like to know.

I have worked with NLB and I understand how it works, but I'm new with
MSCS, and I must need to know to cluster SQL servers.

In SQL 2000, the cluster can be active/pasive or active/active.

If it is active/pasive, one of the two nodes, assumes all work, and
the second node is waiting that the first node goes down, when that
happens the second node assumes all work, this is the failover. Every
node has got one IP and the two nodes have a IP that they share (
Virtual Server), like NLB.

The ASP applications connect to the IP of Virtual Server. No problem.

The cluster is transparent to the ASP aplication.

But if I have active/active mode, the application must see two SQL
Server, not one like active/pasive mode, it's true ? The cluster isn't
transparent to the ASP aplication ?

The developement of the ASP application is different that the
active/pasive and active/active modes ?

With MSCS is possible to make the system scalable or only the failover
is possible ? If it's possible the scalability, is necessary to modify
the ASP developement or it's transparent ?

I read that MSCS is necesary that the servers must be joined in a
domain, it can't work in a Workgroup.

If I install AD in the 2 web servers, the performance will decrease,
there won't be users and permissions, it's only a web portal.
Is it possible to work in a Workgroup ?

And at the end, give me your opinion about :

- Install SQL 2000 SP4 or SQL 2005 ?
- Install MSCS or a third party software, like Computer associates ?

Thanks in advance,