Opera Software, the third-largest Web browser maker, released the latest version of its Windows browser software for free download Wednesday, hoping to challenge the dominance of its rivals. The Opera for Windows 5.0 browser contains news and email clients, integrated Web search and instant messaging functions, and supports plug-ins. It is a 1.89MB download, with code to enable Java and Java plug-ins adding 7MB to the file size. In comparison, a full install of Internet Explorer version 5.5 requires 111MB of hard disk space, and a minimum install requires 45MB. A complete install of Netscape Communicator version 4.7 requires 14MB on the hard disk. "With a smaller browser, you leave more room in your RAM (random-access memory) for data," said Jon von Tetzchner, Opera's chief executive officer. "And with the file size as small, it opens the door for Opera to run on smaller devices." Opera has versions for the EPOC operating system used in mobile telephones and other portable devices, as well as a Linux version in beta-test stage, a Macintosh OS version and a version for BeOS. Tetzchner said he would consider working toward a PalmOS version when RAM and screen size improves on personal digital assistants. Microsoft’s Internet Explorer and AOL's Netscape products lead browser sales worldwide, in large part because personal computers are often sold with the software bundled in, or can be downloaded for free. The free version of Opera carries banner advertising, while the browser without ads costs US$39. "People say they would use Opera, if they wouldn't have to spend money to buy it," said Tetzchner. "This gives them an option." He said Opera has between one and two million users of its browser software worldwide.