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Computerworld - Everyone likes to try new and shiny technology toys like the Windows 7 beta, but when the price is having to replace your existing operating system, that's too much for most people. That's when being able to use a virtualization program can come in darn handy.

To test out how well Windows 7 works on a virtualized system, I decided to use Sun's VirtualBox software. While there are, of course, other virtualization programs out there, such as VMware's Workstation and Parallels Desktop, VirtualBox has two significant advantages over the others. First, it's free. Second, you can use it with several operating systems, including Windows, Linux, Macintosh and OpenSolaris.

In my case, I decided to use VirtualBox to run Windows 7 on two Dell Inspiron 530S systems, one running Windows XP Pro SP3 and the other running MEPIS 7 Linux. Each PC came with a 2.2-GHz Intel Pentium E2200 dual-core processor with an 800-MHz front-side bus, 4GB of RAM, a 500GB SATA drive and an Integrated Intel 3100 Graphics Media Accelerator. While not powerful systems, these proved to have more than enough CPU power to run both their native operating system and Windows 7.

Running VirtualBox

VirtualBox comes in two editions. The full VirtualBox is free for personal use and evaluation, but doesn't come with the complete source code. VirtualBox OSE (Open Source Edition), also free, does come with the source code and includes several enterprise-level features, such as an RDP (Remote Display Protocol) Server and USB support. (Other virtualization applications, like Xen, require tweaking before they'll support USB.) Both versions can run Windows 7.

In general, you'll need at least 1GB of RAM to run VirtualBox and a guest operating system. More RAM is always better. In my testing, I found that Windows 7 would actually run on as little as 512MB, while Vista really needs at least 1GB of its own.

VirtualBox should run on any recent CPU, but it does best with high-end processors that support hardware virtualization enhancements such as Intel's VT-x and Advanced Micro Devices' AMD-V.

The first step is to download a copy of VirtualBox. To run Windows 7 successfully, you'll need at least VirtualBox 2.1.0 -- I ran it on the latest version, VirtualBox 2.1.2.

If you're a Linux or OpenSolaris user, you can also obtain a copy using your software package manager program. VirtualBox supports openSUSE, Fedora, Ubuntu, Debian, Mandriva, PCLinuxOS, RHEL (Red Hat Enterprise Linux), SLE (SUSE Linux Enterprise) and Xandros. You can also find additional support, both for specific operating systems and in general, in the FAQ file and in the User Manual (PDF).

On Windows and Mac OS X, installation requires little more than clicking on the installation file and letting it run. It's a bit more complicated on Linux and OpenSolaris. On Solaris, you need to compile the program. On Linux, you'll need to follow some additional steps, which are described in the Linux download section.

Finally, if you need more guidance, you can find step-by-step instructions for VirtualBox 2.1.0 at the Two Guys Tech site.

Setting up the VM

Your next step is to set up a new virtual machine for Windows 7. You do this by clicking the New button, which will then ask you how big a hard drive you want for the operating system. The default is to give it a 20GB virtual hard drive. With Windows 7, I decided to give it a more generous 40GB. You can also let VirtualBox dynamically determine how much hard drive room an operating system can have, but I prefer to decide for myself.

This done, you set up how much RAM and video memory Windows 7 can have. I prefer to give the operating system an ample 1GB of RAM and 128MB of video memory. You can get by with less, but you'll start noticing system delays.

VirtualBox also lets you set up 3-D graphics acceleration and access optical discs, USB devices, shared drives and so on through its main interface. You can set this up after you have Windows 7 installed, but I prefer to get this basic configuration out of the way first.