Munich  - It's hard to be 100 per cent consistent. Computer operating systems are no different. The Mac OS tends to be very easy to use, particularly for users who don't need to make major changes to their system. Yet, some programme types just aren't often made for the Mac. One way to circumvent this is virtualisation.

"Virtualisation involves one computer with additional virtual computers running on it, each independent of one another," explains Sven Ahnert, an IT expert and technical book author. The interesting aspect is that no additional hardware is required. With the right software, one standard Mac OS X machine can also run Windows XP.

There's a bit of a dearth of tax and finance programs like Quicken for the Mac OS, for example.

"Those programs run terrifically using virtualisation," says Walter Mehl from Munich-based Macwelt magazine. When working with simple applications, there is almost no difference in speed between programs running on virtual machines and those running on real ones, Walter Mehl explains. Intensive software like that used for 3D design runs "unreasonably slowly" under virtualisation, however.

You have to remember that virtualisation involves two operating systems running on the computer at once, Mehl says. That means that at least two gigabytes of RAM are needed. Older Macs or Macbooks without a graphics card of their own are not well suited for the task, Mehl says. Another prerequisite: a Mac with an Intel processor.

One well-known virtualisation program is called VirtualBox. It is made by software maker Sun and is available at no cost. VirtualBox is available not just for Mac OS, but for Windows, Linux and OpenSolaris as well. VirtualBox can simulate even more systems than those: the list includes various versions of Windows, Linux and Mac OS, as well as DOS, Solaris, OpenSolaris and OpenBSD.

There are two big names in the commercial virtualisation field: VMware and Parallels. Each has released new commercial virtualisation programs for the Mac, Fusion
(VMware) and Parallels Desktop 4.0 for Mac. Both manufacturers offer a large series of programs - many of them at no cost. Even so, it's worth considering beforehand whether you'll need the functions found only in the pay-versions.

One interesting aspect is the snapshot functions, says virtualisation expert Ahnert. It allows for an instant capture of the state of the virtual system. This allows you to return back to a specific backup point, if the system ends up having problems. Regardless of whether purchased or cost-free, users are well advised to always make a backup before working with virtualisation software. (dpa)