User Account Control

Non-admin accounts are the default in Windows Vista - this feature is known as User Account Control, or UAC. The operating system will prompt for administrator privileges when required (this has been the cause of some controversy in early betas):

Here's a summary from the Fundamentals section in MSDN's Windows Vista Developer Center:

Windows Vista introduces an improved security model that reduces a system's vulnerability to attack while still empowering applications. In particular, it makes the new User Account Protection (UAP) the default user account, and provides an easy-to-use temporary-privilege elevation model. As a result, malware installations are reduced and more OS functionality is made safely available to non-administrators.

There are more details in the TechNet paper "Windows Vista Security and Data Protection Improvements".

This feature has been through a couple of name changes - first it was LUA (as in Windows XP), then it was User Account Protection, and now it is User Account Control.

The team has a blog at http://blogs.msdn.com/uac/, and have taken part in a Going Deep interview on Channel 9.