Microsoft Windows and Office software licenses are likely to be the most expensive elements in any virtual desktop infrastructure (VDI) roll-out, according to The Hypervisor research.

VDI systems replace traditional PCs with virtual machines running desktop software. Each user has their own dedicated virtual machine (VM), and users connect to their VM using one of several remote desktop protocols, such as Microsoft RDP or Citrix ICA.

Advocates say this approach makes the desktops easier to manage than traditional corporate PCs, particularly when it comes to provisioning, backup and disaster recovery. Many of them argue the cost of ownership would also be lower than using desktop PCs systems.

While this may be true, research by The Hypervisor indicates the biggest expense in a VDI deployment may well the cost of Microsoft Windows and Office software, particularly in organisations that prefer to use Windows XP instead of Vista.

Although Microsoft Vista was launched in November 2006, many IT organisations have standardized on Windows XP as their desktop operating system and are reluctant to use PCs running Vista. This is because many users find it difficult to adapt to Vista if they are experienced with Windows XP, and many IT managers are wary of Vista’s increased appetite for RAM and storage.

However, Microsoft recently withdrew boxed copies of Windows XP from sale to corporate customers, which has had a particularly dramatic effect on the price of VDI based systems running Windows XP.

Microsoft license terms mean small and medium sized firms building new VMs running Windows must buy a boxed copy of Windows for each VM. Those that want to run XP must buy a boxed copy of Windows Vista Business Edition and a Windows Vista Upgrade license, which entitles that PC to be downgraded to Windows XP Professional. The lowest prices we could find from a reputable Microsoft reseller in the UK were £136.43 for Vista Business Edition and £141.64 ex. VAT for the Vista Upgrade option. When these are added to the price of Microsoft Office Standard Edition, which is £282.02, the cost of Microsoft licenses is £560.09 ex. VAT per desktop.

In comparison, we estimate a suitable server platform to support 20 users would cost around £5,000, or £250 per user. Similarly, the price for the VMware View VDI suite, which includes the VMware ESX hypervisor, VirtualCenter management console and all the tools needed to make a top grade VDI system, is $250 per user.

Clearly at these prices, the cost of Microsoft XP and Office licenses is higher than the combined cost of server hardware and virtualization software.