Using virtualization to run multiple operating systems on a single physical computer was once mainly the domain of ubergeeks and IT administrators, but these days there's much more widespread interest in the technology, whether as a means to test a planned software deployment, kick the tires on a new OS, or just to continue using an application designed for a now obsolete operating system.
Virtualization's increase in popularity is in part due to Microsoft's decision several years ago to offer its Virtual PC 2004 software (which it acquired from now-defunct Connectix) for free. Some users soon found that there was a catch, however, because VPC 2004 didn't work particularly well with Windows Vista, whether as the guest (virtualized) operating system or as the host OS running natively on the system.
With the new Virtual PC 2007, Vista-related issues are no more (at least technical ones — more on that in a moment). While VPC 2007 doesn't address all of VPC 2004's limitations — nor for that matter does it offer the same level of features as virtualization products like Parallels Workstation or VMWare Workstation — it does handle the basics well. And like it's predecessor, VPC 2007 is available free of charge, which for many will be reason enough to try it.
Licensing Issues
Before you consider using VPC 2007, it's important to be aware of Microsoft's fairly restrictive licensing requirements for the software. For starters, VPC 2007 is only licensed to run on the following versions of Windows — Vista Business, Enterprise, or Ultimate Edition; Windows Server 2003; and Windows XP Professional and Tablet Editions.
You may notice that Windows XP Home and Windows Vista's Home Editions (Basic and Premium) are conspicuously absent from this list. If you try to use VPC 2007 on any of those, the install routine will admonish you with a warning dialog, but surprisingly, you can click away the warning and proceed with the installation anyway. (Actually, it's not that much of a surprise, considering VPC 2004 does the same thing when installed on XP Home). To tie your hands even further, the EULAs for both Vista Home Basic and Premium explicitly forbid their use within any virtual environment, not just with Virtual PC 2007.
There has been a fair amount of angst about Microsoft's decision to restrict the use of both VPC 2007 and Vista for what are believed to be marketing rather than technical reasons. Microsoft's policy may yet change — the company has reportedly come close to amending it at least once already — but for now, you should be mindful of the various license restrictions that come with the software.
Setup and Virtual Machine Configuration
After downloading and installing Virtual PC 2007, the software makes setting up virtual machines for guest operating systems quite simple. You pick the operating system you want to install from a list provided by a VM wizard, and VPC 2007 then configures your VM to use an appropriate amount of memory and disk space.
This being a Microsoft product, the guest OS menu consists primarily of other Microsoft products (Windows 98 through Vista for client operating systems, plus NT/2000/2003 Server), but since the choices merely reflect minimum RAM/disk amounts, you're not necessarily limited to installing the OS specified.
Initial values for either RAM or disk space can be adjusted later in the wizard, or even after a VM has had an OS installed. When it comes to disk space, VPC 2007 uses dynamically-sized virtual disks (.VHD files), in which the amount of space indicated (anywhere from 8 - 64 GB) actually represents the maximum the disk can set aside. This helps conserve space by allowing dynamic virtual disks to start out small and consume additional space only as needed.
To set up a guest operating system, you can use a newly-created virtual machine to capture the DVD drive containing the OS disc, or else mount an ISO image of the disc (in either case, you must have a licensed and unused copy of the operating system). We installed multiple versions of Windows (XP Home and Professional, plus Vista Ultimate) plus SuSE Linux 10 without any problems. Although it worked fine with Parallels Workstation, graphics and mouse recognition problems prevented us from successfully installing Ubuntu 7.04.
By the way, if you already have VPC 2004 (with Service Pack 1) installed on your system, VPC 2007 can install on top of it and will identify and work with any virtual machines you already have. When we performed an upgrade from VPC 2004, all existing virtual machines (a half-dozen) were recognized and ran without a hitch.
