Windows Vista introduces a host of changes to improve the security, reliability and general user experience compared with previous Windows releases.

Vista is available from 30 November for volume licensees, while companies looking to get the operating system pre-installed on new PCs will have to wait until after January 2007. Microsoft customers will find Vista a worthwhile upgrade, although there are few features compelling enough to make the case for an immediate migration.

Vista will ship in several editions, with Vista Business and Vista Enterprise the most appropriate for companies. Vista Enterprise is only available to volume licensees.

We tested the 32bit release version of Vista Ultimate, which includes advanced features such as the BitLocker disk encryption tool, but lacks the Unix application compatibility tools and multi-language support found in Vista Enterprise.

Vista’s basic system requirements are an 800MHz processor and 512MB memory, while Premium features such as BitLocker require at least a 1GHz processor, 1GB memory, and a graphics adapter compatible with Vista’s new Windows Display Driver Model (WDDM).

Our tests suggest that memory is the main factor affecting Vista’s performance, and firms should regard 1GB as the bare minimum for new PCs. We tested on several systems, including a Fujitsu-Siemens 3GHz Pentium 4 PC with 512MB memory, and a Dell Optiplex 745 Core 2 Duo 2.4GHz system with 1GB memory. Vista ran fine on the Fujitsu, but without the Aero user interface, while performance was noticeably better on the Dell.

On the Dell, we found that Vista still did not install drivers for the graphics functions of its Intel Q965 chipset, and we were forced to manually install drivers taken from Intel’s web site, as we did with the beta code.

Our tests also suggest that most current business applications should run with no problems under Vista, although low-level tools such as antivirus will almost certainly require upgrading to new Vista-compatible versions.

Vista’s user interface does away with the standard Luna theme of Windows XP and instead adopts a look and feel closer to the classic Windows desktop.

Users with higher performance systems can enable the Aero user interface, which renders the edges of Windows translucent, as if they are edged with smoked glass. Microsoft says the effect is designed to make the contents more prominent.

Aero also enables three-dimensional shuffling of open windows. Pressing the Windows key + Tab morphs open windows into a 3D stack, and lets users cycle through windows like flicking through cards in a Rolodex.

On systems that do not meet the requirements for Aero, users see the Standard or Basic user interfaces. These are similar in general look and feel, but lack the transparency effects and the “Flip 3D” window management effect.