Version 6.5 of VMware's popular Workstation package has lots of new features packed in despite not being a full jump to version 7.0.

Launched last week, the headline new features are enhanced VMware Assured Computing Environment (ACE) authoring, and a so-called Unity mode whereby users can better integrate their favourite guest applications with the host system.

Workstation lets users install and run so-called 'guest' operating systems on desktops and laptops which run Windows or Linux as the main operating system.

There are many advantages to this. Firms can run older unsupported operating systems with legacy applications not supported on newer operating systems, while security can be tightened with a 'snapshot' capability which allows users to roll back quickly to a previously safe state.

VMware's ACE system gives IT managers the ability to build a virtual OS, which can be locked down and then distributed to end users, subject to certain licensing constraints.

With Workstation 6.5 VMware claims that ACE's authoring features are now fully integrated and that "no special ACE Edition is required".

Companies using Workstation in a test and development environment will probably use a high-end system with over 2GB of system memory and multiple processors.

As an example, when running Workstation 6.5 on systems with 512MB or less we were constantly having to reduce the memory usable by our guest operating system, which on several occasions with Linux operating systems meant that we ended up with the command line interface rather than the standard GUI.

Guest OS installs are limited to two processors, a maximum of 8GB of system memory and a maximum of 10 network adapters. Compatibility with VMware's ESX server is limited to version 4.xx and below of Workstation.

We installed Workstation 6.5 on a desktop system running Windows Vista Enterprise and a laptop running XP Professional.

Version 6.5 is just as easy to use as earlier versions, and we installed a variety of Windows operating systems (2000, XP, Vista) and several Linux distributions, like Oracle's Enterprise Linux v5.2 and the Community ENTerprise Operating System 5.2, with no unsolvable problems.

Other new features include accelerated 3D graphics using DirectX 9 shaders when using Windows XP Professional guest operating systems, and Linux or Windows 2000, XP and Vista host operating systems.

VMware has now made it possible for users to stream a virtual machine from a web server and power it on before the download completes.

There is also a Linux version of Workstation 6.5 which we'll be looking at later in the full review.