Windows Defender, an anti-spyware program that was available as a download for Windows XP, comes as an integrated part of Windows Vista. Windows Defender can do a quick scan or a deep scan of your hard drives to find hidden threats. Windows Defender also provides detailed information about your computer in Software Explorer. It monitors startup programs, currently running programs, network connected programs and winsock service providers and looks for problems that might affect the security and privacy of your computer. With Windows Defender tools you can also quarantine items that are a potential threat to your computer, and allow items that you don't want Windows Defender to scan for.
Sources:
"Windows Aero," http://www.microsoft.com/windows/windows-vista/features/aero.aspx
"Search and organization," http://www.microsoft.com/windows/windows-vista/features/search-and-organization.aspx
"Windows Media Center," http://www.microsoft.com/windows/windows-vista/features/media-center.aspx
"Windows Defender," http://www.microsoft.com/windows/products/winfamily/defender/default.mspx