VMware has announced an upgrade to its application virtualization software, which aims to reduce the cost of deploying new desktop programs to end users.

The software allows IT departments to package a desktop application into a single executable file, which can then be deployed and run by the end user without altering the host machine's operating system, such as its file system or registry files.

The idea is to avoid the software conflicts that can "break" existing desktop applications, and to reduce the amount of testing IT departments have to do before they deploy a new application.

VMware bought the software earlier this year when it acquired a company called Thinstall. On Tuesday it announced that it has rebranded the product as ThinApp, and said a new version, ThinApp 4, will go on sale within 30 days.

IT departments can package an application with ThinApp and then deploy the package on computers running almost any version of Windows, including XP and Vista, said Jerry Chen, VMware senior director for enterprise desktops. ThinApp can also run two versions of the same program, so a user could run Internet Explorer 6 and 7 on the same desktop if they needed to.

One drawback has been that virtualized applications can't communicate with each other, because they operate in a their own virtual software "bubble." If a user is running virtualized Microsoft Word, for example, and clicks on a Web link in a Word document, the application can't call on Internet Explorer to open the Web page.

In ThinApp 4, a new feature called Application Link allows administrators to create these links between virtualized applications. An administrator could create a separate package for a Java or .Net component and share it across multiple virtualized applications, Chen said.

The other main enhancement is Application Sync, for delivering bug fixes and other updates. "All I have to do is virtualize the new version, post it on a Web server, then the existing version detects that there's been a change and downloads the differences," Chen said.

Michael Rose, a research analyst with IDC, said products like ThinApp have a lot of promise, but he said they may be ahead of the market because most people are still coming to terms with the basics of desktop virtualization.

"VMware has done a good job in getting out ahead of this but I don't think many people are considering it just yet," he said. "Desktop environments are really complex and I don't think there's enough maturity in these platforms yet to see really broad-based adoption. There will be, but it's a matter of time."

Ronni Colville, a vice president and distinguished analyst with Gartner, was more upbeat. She said application virtualization, while it doesn't get as much attention as other virtualization technologies, could be significant in the near term. Gartner predicts that 50 percent of large businesses will use application virtualization by 2010.

ThinApp will compete with Microsoft's Application virtualization software, formerly called SoftGrid, which it acquired when it bought Softricity. Rose and Colville both noted that the Microsoft product is available only to customers who sign up for its Software Assurance licensing program, which will limit its appeal.

In addition, the Microsoft software, along with a comparable product from Citrix, both require a greater investment in server software before customers can use them, the analysts said. ThinApp can be used independently of other VMware products, and it works with existing PC management tools from BMC Software, Avocent/LANDesk and others.

In the future, VMware could potentially combine elements of ThinApp with its Virtual Desktop Infrastructure (VDI) product, Colville said. VDI is for a different form of virtualization, in which a desktop image is hosted on a server and accessed remotely by end users.

These hosted desktops tend to be "all or nothing," Colville said, with a large software configuration being streamed over the network. The ThinApp technology could allow VMware to deliver discrete parts of the desktop image wrapped in "virtual bubbles," which could make the delivery more nimble, she said.

Client licenses for ThinApp 4 are priced at $39 per desktop, Chen said. Customers will also need the ThinApp virtualization Suite, for packaging applications, which is priced at $5,000 and includes 50 client licenses. Rose said Thinstall customers he spoke to told him that packaging applications for delivery with ThinApp is relatively easy.