So a few years ago the big thing was the introduction of the Virtual Machine.  Two companies tend to control this market, VMWare and Microsoft's VPC.  There is plenty of existing stuff out there on how virtual machines are changing the way people and companies look at hardware. Two things I wanted to point out for the desktop version of these products. 

The first deals with performance.  If you are going to use a virtual operating system you are in essence going to run two PCs on your machine.  To make this work better try to get enough memory (at least a gig) so that each machine can have about 512MB and try to make sure that you have a processor that supports hyper-threading so each environment can have a dedicated processor.  Finally try to ensure that your virtual machine disks are hosted on a separate drive from the drive hosting your operating system, in fact this is one of the most important performance elements since disk access is and always will be the slowest operation in your system, and having two operating systems fight for time on the same hard drive will just increase any perceived performance issue.

The second topic deals with virual machines on corporate desktops.  This is an important little note that most companies probably haven't thought about.  I'm working with a customer and I just got a notice about how on my next restart the logon script will ensure that an important Microsoft Patch is installed on my machine.  This company happens to place their developer's virtual machines in their domain, so in theory my virtual PC will be updated the next time I login on it. Which is the issue, with virtual machines I have the option to Suspend the operation of my OS and then come back tomorrow, restart my base PC and just resume my virtual machine without restarting or logging in.  I've had virtual machines on my desktop where I've worked on some part time project over the course of weeks without a restart.  So think about the model where a patch will be installed once I restart - for the normal user who logs out at the end of the day the maximum delay is rarely more then a day or so, but for a virtual PC it might be weeks before that logon script is rerun... so what do you think will happen first - corporate IT staff will learn to update their virtual machines with the latest patches or large corporations will ask for an option to prevent their IT staff from suspending a virtual machine.