Two start-ups hoping to profit from virtualization are giving details of new strategies this week. It's a sign that the technology, while a hot item, doesn't mean easy profits.

Virtual Iron and XenSource both have altered course with their virtualization products, which is software that lets a single computer run multiple operating systems simultaneously. Virtual Iron has scrapped its own virtualization software in favor of the open-source Xen project. Meanwhile, the leader of that project, XenSource, is steering away from management tools and aiming squarely for virtualization leader VMware.

The two companies are describing their new strategies at the LinuxWorld Conference and Expo in Boston this week. And with more news in the area from VMware, Microsoft's Virtual Server group and SWsoft, the show might well be called VirtualizationWorld.

If imitation is the sincerest form of flattery, VMware executives might blush at the strikingly similar rhetoric from Virtual Iron and XenSource.

"The market really wants a competitor to VMware," said Simon Crosby, XenSource's co-founder and chief technology officer.

"It's time for a company to step up and be a viable commercial competitor to VMware," said Virtual Iron Chief Executive John Thibault.

It's no surprise why competitors are angling for advantage. A February Forrester survey of 1,221 customers with at least 1,000 employees found that 41 percent of North American customers are using virtualization already or are planning pilot tests. And 60 percent plan to spend more money on the technology in the next 12 months.

VMware leads the market, the study found, with 43 percent of customers considering it most often for x86 server virtualization, compared with 24 percent for Windows Virtual Server. Xen "is not yet on the radar for customers," the report said.

Virtualization, in the form most widely discussed these days, lets a computer run many operating systems simultaneously and therefore lets administrators replace several largely idle servers with one efficiently used machine. The technology works by fooling programs into thinking that they're running on real hardware, when they actually are running on a virtual layer called a hypervisor.