Taking the Virtual Machine Approach

If you need access to multiple OSs primarily for testing purposes rather than for long periods of work, there’s another way to use multiple OSs without the hassle inherent to multiboot setups. In fact, you can even use multiple OSs simultaneously on the same computer. It’s done with a setup called a virtual machine. This is an old concept—IBM used it on its mainframes as far back as the 1970s—and it’s making a big comeback, thanks to today’s fast processors and huge hard disks. A virtual machine program emulates (simulates) in software all the hardware functions of a PC. It lets an entire operating system (called a guest operating system) run as an ordinary application program on a host operating system such as Windows 7. Because all the hardware functions are emulated, the guest OS doesn’t “know” it’s not in complete control of a real physical computer. When the guest OS requests access to a hard disk, display card, network adapter, or serial port, the virtual machine program calls upon the host OS to actually carry out the necessary operations.

Even though software might occasionally need to execute hundreds of instructions to emulate a single hardware operation, the overall speed penalty is only 5%–10%. And if a guest OS crashes, it won’t take down your system. You can simply click a Reset menu choice and “reboot” the virtual machine.

Another advantage of the virtual machine programs currently on the market is that they don’t allow a guest OS unfettered access to your real disk drives. Instead, you create a virtual disk, a single large file on your host OS that contains what a virtual machine sees as a hard drive. With today’s large hard drives, it’s no big deal to create a 15GB–30GB file to serve as a virtual hard drive for an older version of Windows or even Linux.

If you make a backup copy of the file after installing a guest OS on a virtual disk drive, you can return the guest OS to its original, pristine state just by copying the backup over the virtual disk file. You can even boot up a guest OS, start a bunch of applications, and save the virtual machine in this exact state. When you want to use it again, just fire up the whole system from that point. If you’re a tester or experimenter, a virtual computer can save hours of time installing, reinstalling, and rebooting.

Of course, you still need separate licenses for all the extra Oss you install, but a virtual machine can let you run as many Oss and as many configurations of these OSs as you like, separately or simultaneously. And all this comes without the hassle of editing the Windows 7 boot menu or worrying about partitions. If full-blown virtualization sounds interesting, check into these products:

• VMware, now an EMC company, located at www.vmware.com. VMware Workstation was the first commercial system to emulate a PC on a PC. It’s the most “industrial-strength” PC emulator available. You can get a 30-day free trial of VMware Workstation from the VMware site. Or, you can use the free VMware Player version to run virtual computers set up by others.

• Microsoft Virtual PC. Microsoft bought this program from Connectix Corporation. Versions are available for Windows and for the Mac; check out www.microsoft.com/virtualpc.

The Windows version of Virtual PC 2007 is a free download that anyone can use. In general, the experience for non-Windows OSs on Virtual PC is not as good as with VMware Workstation. However, it’s free, so we can’t complain too much. Be sure to download the Virtual PC extensions and give a Windows 7 Virtual PC at least 1GB of memory (a setting in Virtual PC) for it to run with any appreciable speed. This requires that at least 1.5GB of physical RAM in your host PC.

Source of Information : QUE Microsoft Windows in Depth (09-2009)