With billions spent on hardware, software, and services each year, the enterprise Unix market can support more than one major player. Sun Microsystems Inc. is top dog with a commanding lead in unit sales, revenue and mind share. Hewlett-Packard Co.'s expertise in health care and scientific communities keep the company in the top three, but that advantage isn't ironclad, especially up against Sun's ruthless sales force. To overcome the inertia of its flagship OS, HP has opted to open up HP-UX to allow the best of both worlds: Linux's populist appeal and HP's bullet-proof, if staid, image to create HP-UX 11i, Hewlett-Packard's most ambitious operating system to date. On the hardware front, HP joined forces with Intel Corp. to create the Itanium, a 64-bit processor that the companies hope will shape the future of open systems.