Until the release of Windows 7 in late 2009 or early 2010, Microsoft's Windows Vista is the company's flagship product and operating system. It's the successor to reigning king Windows XP, and builds on the XP foundation with a totally rehabbed user interface (called Aero) and a number of new security features. Like XP and the other versions of Windows before it, it's responsible for most of the activities of the computer it's installed on, and most other programs run by communicating with it.

The most notable new security feature is called User Account Control (UAC). When UAC is enabled, any program that wants to access or modify critical system files (the common targets of spyware, viruses, and other ailments) must first prompt you and check if it's okay. If you're not logged into an administrator's account, it will ask you to enter an administrator's password. Vista also overhauls search by carefully indexing all important directories and files on the computer so you can type in a search anywhere and get near-instantaneous results. Both of these features were previously found in other operating systems, including Apple's Mac OS X and various distributions of Linux.

Other improvements: improved tools for connecting with devices like portable media players and other computers, a completely redesigned Start Menu, updated content creation and media tools, and a greatly improved aesthetic appearance, including transparent windows, live video thumbnails, and a new, prettier method of switching between active windows called Flip 3D.

Impressive as many of these features are, many users have reacted negatively to Windows Vista because of its high memory usage (which makes it unusable on some low-end computers, and comparatively sluggish on even mid-range ones) and invasive security measures. For example, User Account Control is often called an annoyance, as it's an all-or-nothing deal; you can either turn it on or off, but you can't strike a compromise. Because of complaints like those and a troubled public relations campaign, Vista has failed to live up to the success of its predecessor, although it still has managed to make its way onto over 20% of computers worldwide.

Vista is available in four editions, each with a different set of features: Home Basic ($199.95), Home Premium ($259.95), Business ($299.95), and Ultimate ($319.95).