Shortly after Microsoft bought out the Virtual PC franchise from
longtime Mac developer Connectix in 2003, it hit a stumbling block -
VPC 6.x didn't work on Apple's new high-end G5-powered hardware.
Just as English is written from left to right while Hebrew and
Arabic go from right to left, Mac and PC processors read bytes of data
in opposite directions. G3 and G4s support a "pseudo little-endian
mode" feature that increased performance when emulating a Pentium-style
CPU. While faster and more powerful overall, the G5 lacked that mode,
making earlier versions of VPC-Mac unusable on Apple's flagship
systems.
Rewriting the program to provide G5 support, VPC 7 was pretty much
ready this past summer, but Microsoft chose to hold off its release
while awaiting Windows XP Service Pack 2, preferring to give its
customers the security features built-into that Windows update. The
September release proved to be well timed, coming out at about the same
time as Apple's release of the iMac G5 that brought the G5
processor to a wider market.
VPC 7 is being released on its own in a variety of versions and as
part of Microsoft Office Professional 2004 - the part of MS Office Pro
that differentiates it from the previously released Office Standard.
VPC pricing depends on the Windows version that is bundled along with
it: With Windows XP Pro or Windows 2000 Pro, it lists for US$249; with
XP Home, its US$219. If you want to roll your own operating system,
it's US$129. And owners of VPC versions 5 or 6 can upgrade for
US$99.
Hardware requirements are relatively steep: Microsoft suggests at
least a 700 MHz G3 or better, OS X 10.2.8 or 10.3.x, 3 GB of
free drive space, and at least 512 MB of memory. More is better -
that's because VPC is trying to emulate a complete Windows PC on your
Mac. You'll need enough RAM to keep your Mac's operating system happy
plus enough memory for the emulated PC, and modern versions of both
OS X and Windows can never have too much memory.
I tested VPC 7 on an iBook G4/800 with 640 MB of
memory, a system relatively close to Microsoft's minimum
requirements.
While it's an interesting technical achievement to make your Mac
pretend to be a PC and good fun to watch Windows boot up in a window on
your OS X desktop, why bother?
Microsoft's polling suggests that more than half of surveyed Mac
users expressed a need to access Windows-only software, at least some
of the time. Many businesses use Microsoft's Access database, for
instance, included in the Windows Office Professional product and not
available in a Mac version.
Web developers need to be able to see how their output will look on
a PC running the Windows Internet Explorer; viewing it in the Mac
version isn't good enough. (And sadly, too many bank and e-commerce
sites will only work with Windows Internet Explorer. My daughter was
unable to register for her college courses from her Mac; she had to
move to a PC to sign up for this term's classes.)
I moderate an online discussion group hosted on FidoNet running on
several hundred old-style BBSs worldwide. While I can log on and view
messages using telnet on OS X's Terminal, it's more convenient to
download entire packets of messages and read and respond offline. I've
found software to do that in Windows, but not for the Mac.
Sure, you could buy a low-end PC for only a couple of hundred
dollars more than the cost of a copy of VPC, and it would offer better
performance than VPC (at least on my iBook!), but it wouldn't allow
access to the Mac clipboard or easy access to files on the Mac. And it
would take up a lot more desk space.
Assuming you've got powerful enough hardware with enough memory and
free drive space, creating a Windows PC using VPC is pretty
straightforward. If you've got a copy with a bundled operating system,
it's a matter of installing VPC, then choosing the menu option to
create a new virtual PC. Because the copy of Windows bundled with VPC
is preconfigured for your virtual hardware, it's faster than installing
Windows on a real PC.
Alternatively, you can create a new PC and install the operating
system of your choice, including older versions of Windows and some
versions of Linux (some Linux distributions will not work, and
Microsoft's support for Linux is, not surprisingly, limited).
Installation with the new version has been improved with automated
wizards taking much of the guesswork out of the process - at least when
installing Microsoft-supported operating systems.
Also new and improved is support for Mac printers. OS X 10.3
users will find that their system printers are automatically used by
VPC, meaning there's no longer a need to set up printing
separately.
Running Windows applications can optionally show up in the OS X
Dock. Clicking the red close button on the OS X window now
defaults to Fast Save, putting VPC to sleep, enabling a quick restart
next time.
Microsoft promises, along with G5 support, better performance with
this version: 10 to 30% faster startup, refresh, and response times,
along with taking advantage of Mac OS X's OpenGL graphics routines for
more responsive graphics handling.
Comparing the new version to the older VPC 6.01 on my iBook,
however, the improvements weren't dramatically noticeable. As with
previous versions, if the only-on-Windows software you want to run is
games, get a PC - you won't find VPC's graphics performance (or rather,
lack of performance) acceptable.
And at least on my hardware, Microsoft's latest Windows XP was
pretty sluggish - so sluggish that I much preferred using the older
Windows 98. Designed for an older generation of (real) PCs, it was much
happier with the virtual PC that I could offer it.
Still, if you're one of Microsoft's estimated half of Mac-owners who
need to run a Windows-only application now and then and you don't have
a real PC handy, VPC is probably worthwhile, especially if you want to
use a Mac at work where the company requires you to use a custom-built
corporate Windows application.
If you've got a G5 Mac, such as the new iMac, Virtual PC 7 is
your only choice. But if you've already running a recent VPC version,
I'm not sure there's enough new and improved in version 7 to justify
the US$100 upgrade cost. 
