For decades most businesses have accepted that every employee needs a PC with its own operating system and its own applications, all sitting on its own hard drive.
But all that could be about to end if the virtualisation trend sweeping through data centres hits desktops with the same force.
Desktop virtualisation is in effect a rebadging of client computing. This model - dominated by Citrix -- has worked best in enterprises with large desktop fleets or companies with many small offices which would require a lot of manpower to provide IT support.
New technology from VMWare, Wyse and Microsoft, and the emergence of cloud computing, which could also be described as a client computing model, has reintroduced the concept to businesses that fall outside those categories in the small to medium business market.
There are several ways to virtualise a desktop, from applications through to the whole operating system. Each method has advantages and disadvantages, but a common goal is to reduce a major cost to businesses of all sizes: desktop maintenance.
Maintenance can chew up an enormous amount of the average IT budget. Patching and updating every anti-virus program, operating system and applications on every PC in an office takes a lot of effort if done manually or a lot of bandwidth if done remotely using automation tools like Kaseya or Hounddog.
Virtualising desktops allows you to perform all maintenance in the data centre itself, either to a single image or multiple images, and the machine used by the end-user in effect becomes a terminal.
"The desktop should just be a videocard and it's just playing what's happening somewhere else," says Wyse's Ward Nash (pictured).
But desktop virtualisation doesn't necessarily mean the world is moving back to mainframes and terminals just yet. Some vendors give you the option of virtualising certain applications rather than the whole machine.
Employees can use a standard PC, either at work or from home.
Controlling applications from the data centre is also more secure and makes it easier to store and manage data.
It also increases the level of control over what users do with their machines and the applications they run on them.
New security threats which combine social engineering with software hacks are easier to stop from a centralised location than on every device.
Mobile workers carrying around portable devices with company secrets present another vulnerability that can be minimised through virtualisation.
If it all makes such good sense, why hasn't it happened before?
Common complaints were that dumbed-down terminals lacked essential features such as USB connectivity or sufficient bandwidth to play video and music.
These issues have been addressed in the latest terminals, and virtualisation software can also run simultaneously on a standard Windows, Mac or Linux desktop or laptop.
WAN optimisation has also come a long way.
Citrix uses branch repeaters and WAN scalers to compress traffic and cache information to assist desktop and application streaming. Virtualised operating systems mean you can run terminals with Microsoft Office, but without the maintenance overheads of a local Windows OS.
But virtualising desktops can be much more complicated - and expensive -- than virtualising the data centre. The process requires assessing and potentially upgrading the company's entire IT system, from servers through to network.
It is impossible to put a minimum cost of entry to desktop virtualisation as it depends on the current state of a company's IT infrastructure, says Michael Chanter, general manager of professional services division with Frontline, an IT services provider whose typical customer is a 1000-seat plus enterprise.
The price of admission can include virtualisation and server software, better storage and networking, as well as professional services and consulting to put it all into place.
"Some organisations will have a very well controlled environment and they can explain all the application sets and how they manage it, and a good WAN structure in place," says Chanter.
"If it were a greenfield site, for 250 seats you're starting at $100k. If you had annterprise grade SAN that was capable of delivering desktop images, you're already halfway there."
These costs can be offset by reduced storage needs and less maintenance and a lower refresh rate on PCs. Most of the savings come from PC management, says Chanter.
"The man hours to maintain a fleet of desktops is just huge. Now you go back to patching a single image of Vista, that's a fairly trivial exercise."
Virtualisation can also reduce bandwidth costs. "Think about the cost of downloading patches to every desktop to your fleet if it weren't virtualised," says Chanter.
The most important question resellers need to ask customers, says David Wakeman, product marketing manager, enterprise desktop, Australia/New Zealand, of VMWare, is where is the value in operating physical PCs versus virtual ones.
"The value of desktop virtualisation is very different to server consolidation. There's a big opportunity for resellers who can articulate which purchases will change, which processes will become easier. It's much more of a solution sell rather than a hardware sell like with server consolidation."
Client computing has made few inroads into the global market; Wyse estimates it at 6-8 percent of business PCs. But the take-up of cloud computing, from Google Apps to Salesforce, is indirectly introducing similar concepts to the SMB market.
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