The Siebel Alliance Team at Microsoft has hosted several technical workshops over the last 3 years. Thse workshops aim to share leading practices for optimizing your Siebel deployments on the Microsoft Platform. One of the most useful presentation has been where we discuss how Siebel Web Servers, Application Servers and Database Server on Microsoft platform can be optimized for scalability, high availability and performance. Below is a link to a great presentation that every Siebel customer should review.
Siebel Architecture on the Microsoft Platform - www.microsoft-oracle.com