Skype has made available a test version of its latest upgrade, Skype 4.0, which the eBay unit calls its biggest and most ambitious release in its almost five-year history.

"This is the most fundamental change in our product since its inception," said Don Albert, general manager of Skype North America, during a press conference on Wednesday.

Best known as a provider of free and inexpensive Internet telephony services, Skype has redesigned its software in version 4.0 to highlight the other modes of communication it provides.

"We want to let people realize the full benefits of our client software," he said.

The user interface has been redesigned from the ground up to make it cleaner, easier to use and better suited to managing multiple conversations by consolidating, for example, several instant message chats, a video call and a photo file-transfer session into a single screen, instead of having one window for each.

In particular, Skype wants to emphasize video calling, which has grown tremendously in the past two years and now accounts for about 28 percent of all Skype call minutes.

"We have doubled down on video," he said.

Specifically, video calls now start by default with a large screen, and its controls have been tweaked so that a video call can be launched with one click and a companion IM chat session also started with a single click.

Version 4.0 has also been designed to make it easier for users to find friends in the Skype directory, as well as discover existing features they may not know about, he said. In addition, Skype 4.0 recognizes more quickly Skype-certified hardware.

The 4.0 version available now is in "early beta" and very much "a work in progress," but Skype decided to put it out there in order to elicit feedback from users, Albert said.

Skype plans to take its time gathering reactions from people and making adjustments, so it hasn't set a date for wrapping up the beta testing period.