Thanks to Michael Howard for posting about "Windows Vista Security Enhancements". Michael's post links to a white paper that gives a relatively high level technical overview of the security systems of Windows Vista.

The paper titled "Microsoft Windows Vista Security Advancements" is only twenty two pages long so it's a good resource for you to quickly get an end to end view of the new features and improved security architecture of Windows Vista.

Here's a copy of the document's table of contents:


Introduction
Engineering for a Secure Platform
Security Development Lifecycle
Windows Service Hardening
Mitigating Buffer Overruns With Hardware Protection
64-Bit Security Enhancements: Kernel Patch Protection and Mandatory Driver Signing
Secure Access
User Account Control
New Logon Architecture
Easier Smart Card Deployments
Network Access Protection
Protection Against Malware and Intrusions
Windows Security Center
Windows Defender
Windows Firewall
Malicious Software Removal Tool
Security Advances in Internet Explorer 7
Protections Against Malware
Personal Data Safeguards
Data Protection
BitLocker Drive Encryption
Integrated Rights Management Services Client
Encrypting File System Enhancements
USB Device Control
Conclusion