IBM this week plans to make available to customers the latest release of the operating system software for its AS/400 midrange servers. The upgrade, <A HREF="http://www4.zdnet.com/intweek/stories/news/0,4164,2260600,00.html">OS/400 Version 4 Release 4</A>, includes several new features that IBM said are designed for Internet businesses. OS/400 V4R4 is scheduled to be released on May 21.