A Philadelphia developer has rooted out an unfinished feature of Windows 7 that turns any laptop into a wireless access point, allowing other Wi-Fi-enabled devices to share the connection without special software.

Nomadio, which specializes in military network consulting and development, used the new "Virtual Wi-Fi" feature in Windows 7 to create Connectify, a free application that it released as a beta last Friday.

Virtual Wi-Fi was crafted in Microsoft's research group as a way to "virtualize" one wireless card as several separate adapters. The project was discontinued in 2006, but the work made its way into Windows 7 as "Native 802.11 Virtual Wireless Fidelity (Virtual Wi-Fi) object identifiers (OIDs)".

"A year ago, Microsoft talked a lot about this as a big feature in Windows 7," said Alex Gizis, the CEO of Nomadio. "But driver support didn't get finished. The low-level code is in there, but the driver-level stuff isn't. And there's no app or setting in Windows to turn it on."

Explaining that the feature was "half there" in Windows 7, Gizis said his company realized "we have the rest of the software here, in our networking work."

The resulting Connectify differs from the Internet connection sharing that Windows already supports via an "ad hoc" network connection, which lets several Windows computers share a single connection. "For one thing, it shows up as a real wireless access point," Gizis said. "Two, Internet connection sharing has issues. It returns to the default settings every time you shut down a connection. And three, you can join another wireless network and still run the Connectify Hotspot on the same Wi-Fi card."

One application came immediately to mind, Gizis continued. "You're sitting in a coffee shop that charges you for a wireless connection. With Connectify, I can pay for that connection, and still have all my other devices, like my iPhone, connected to the Internet."

Connectify lets a Windows 7 laptop "tether" other wireless devices to a single Internet connection by effectively turning that PC into a software-based wireless router, added Gizis. "We've done a lot of military networking, including a lot of mesh networks," he said, "where special routers connect to each other." That technique, he said, was ideal for keeping in-the-field troops connected to the Internet.

Gizis has used his Connectify-equipped Windows 7 laptop as a wireless access point for his Apple iPhone, for example, and to provide a wireless connection to multiple PCs when only one Ethernet jack was available.

"There are a lot of neat scenarios where this comes in handy," he said. "For example, people can use a wireless printer without any setup, which usually requires that you first plug the [wireless] printer into the computer with a USB cable so it can select the network."

Although the Connectify beta is free to download, Gizis said that Nomadio would likely pin a price on the final, full-featured version when that's ready to release in about six weeks. "I think we'll end up with two-tier model, one that's free, potentially ad-supported, and then sell a full version," said Gizis.

Windows 7 is required on the notebook acting as a wireless hotspot, but any wireless-equipped device, including PCs running Windows XP or Vista, or even Mac laptops, can reach the Web through Connectify without any additional software. Connectify also encrypts the traffic to and from the software "hot spot" using WPA2-Personal (AES) encryption.

The beta of Connectify can be downloaded from Nomadio's Web site.

Apple's Mac OS X already offers a similar feature under the "Internet Sharing" preferences setting.