I'm planning to do a solution. Sorry I'll correct that. some other
company wants my company to do a solution and I'm the one writing the
document. I've no experience with ASP or ISS servers so need a lot of
info.

THere is a database, and a web based front end using HTML and ASP.
There are about 500 users in the system

The database is Microsoft SQL server 2000 sp4.
it uses IIS 5.0
NT Challange / response to authenticate users.
ADO to exchange data between the webserver and the database server.

All running on the one piece of hardware.

Its a project managment system. With about 400 projects going in to
start. and growing with many more. The system will be used heavily
between 9 and 5. What kind of hardware would be required to allow all
users to browse the system during am 8 hour day without overloading the
system.