Now that the Open Virtualization Format (OVF) is available, increasingly more applications will be packaged as OVF-based virtual appliances. But don't hold your breath for virtual appliances based on Microsoft Windows, observers say. Generically speaking, virtual appliances consist of one or more applications, and operating systems pre-installed and preconfigured inside a virtual machine. The recently released OVF provides a standard way to package such appliances. But Microsoft's licensing policies prevent ISVs from packaging appliances with Windows as their operating system. The company allows only certified resellers to package and distribute Windows, effectively preventing Microsoft customers and channel partners from distributing appliances based on a Windows application,, said Jeff Byrne, a senior analyst and consultant with the Hopkinton, Mass.-based Taneja Group Inc.. ISVs that participate in Microsoft's Independent Software Vendor Royalty Licensing Program can place licensed products in their application code, but a lot of users already have Windows licenses and thus end up paying double, said analyst Chris Wolf of Midvale, Utah-based Burton Group. "Most large organizations negotiate their own volume license agreements with Microsoft and would not want to buy an OEM Windows license from a software reseller. They would effectively be paying for OS software that they already own," Wolf said.