The desktop virtualization field is getting more crowded with two new vendors introducing products: one that lets users carry their desktops around on a USB flash drive, and another that delivers desktops through a Web browser.

A start-up called MokaFive on Monday is launching its Virtual Desktop Solution and LivePC products, which let IT centrally manage virtual desktops while giving each user a USB flash drive that lets them pause a computing state on one computer and then resume where they left off on a different PC.

Separately, the vendor Stoneware recently began selling software called webOS that lets a business deliver virtual desktops to its employees through a Web browser.

The vendors likely face an uphill battle with Microsoft, VMware and Citrix (owner of XenSource) all making plays in desktop virtualization. But MokaFive and Stoneware each have a unique way of delivering virtual desktops. Here's a look at both.

MokaFive has released an early version of its technology with a packaged software product as well as a software-as-a -service (SaaS) offering. Version 1.0 will be generally available later in the second quarter.

MokaFive is different than most desktop virtualization products, in which all the execution happens on a back room server, says co-founder and principal engineer John Whaley. Instead, MokaFive virtual machines execute locally through a user's USB drive, so the user is able to work even without a Web connection. At the same time, the system gives IT administrators the power to centrally manage the desktops and apply updates. If a user is working offline, the updates would be downloaded automatically the next time that user is able to connect to the company's network via the Internet.

This model, MokaFive officials say, leverages the benefits of virtualization while also taking advantage of the improving speeds of desktop and laptop computer processors.

"What we wanted to do was make computing a lot easier for the end user and administrator," Whaley says. MokaFive's products include a creation tool that lets administrators design "LivePC" desktops.

The company's technology was developed at Stanford University and was inspired by the Sun Ray virtual desktop product built by Sun Microsystems. Whaley earned a doctorate in computer science at Stanford, where his advisor was professor Monica Lam, who also co-founded MokaFive and is its chief scientist.