VMWare Workstation is a PC emulator which focuses on emulating hardware, similar to Connectix Virtual PC. Unlike just about every real PC available today, it doesn't come with Windows.

For many developers and IT staff, VMWare has become an indispensable tool. It allows a PC running either Windows or Linux to run not just one, but many different operating system configurations concurrently. Just about any OS designed for the i386 platform can be installed and VMWare 4 has pre-configured support for operating systems ranging from DOS to Windows 2003 Server, as well as Netware, FreeBSD and Linux.

When VMWare starts, it emulates a set of generic hardware components, including a VESA BIOS, an Intel 440BX motherboard, an allocated quantity of RAM, a certain amount of hard disk space, a CD drive, network adapter, and so on. Installing an operating system is done exactly as with a real PC; you can boot from CD-ROM or floppy, or image files, so a diskless installation of an operating system can be achieved. Other hardware resources are not emulated but 'mapped' to the VMWare operating system, such as SCSI or IDE CD-R drives, scanners, USB 2 devices, etc.

The beauty of VMWare is that just about any configuration is possible, so Web developers can install Windows 95, 98 and 2000 and maintain different versions of Internet Explorer for testing. Support departments and training facilities, meanwhile, can maintain many different installations and configurations of a product and switch between them easily, in either a windowed environment or full-screen mode. All this can be done with just one PC, meaning it's no longer necessary to use valuable PC hardware to maintain different installations. For these testing environments, a 'snapshot' feature allows a copy to be made of an OS at a particular point in time, which can later be restored, thus encouraging experimentation.

Networking is flexible, to say the least. It can be bridged, where VMWare will take its own IP address on an external network and will operate as a conventional networked PC. Network Address Translation is also possible, where VMWare assumes the IP address of the host operating system. Alternatively, a virtual machine can be networked to the host OS only, and therefore won't appear on any wider LAN/WAN connection.

Networking is available from boot time and works seamlessly. In tests, we successfully installed Red Hat Linux via FTP over a wireless Ethernet card after booting from a floppy image file rather than a physical disk. However, this doesn't even scratch the surface of VMWare's networking support. By using 'virtual switches', many different network testing environments can be set up. This is ideal for IT departments who want to test firewall configurations and server software installations.

As you might expect, VMWare can slow the host machine down, but it will run on quite modest hardware if needed. The most appropriate hardware upgrade is to increase the amount of RAM and then allocate a generous quantity to each virtual machine. Another consideration is hard disk size, especially with the new snapshot feature. A large hard disk means you can create lots of different virtual machines. However, we didn't notice a substantial speed decrease over VMWare 3 on the same hardware.

VMWare 4 introduces some great new features which will ease configuration as well as support new hardware types and operating systems. Some of the new features will only benefit IT staff and 'power users', while other features such as the new 'snapshot' capability will appeal to all.