The atmosphere was supercharged in 1995 when Microsoft ushered in a new era of low-cost 32-bit computing with the introduction of Windows 95. Late-night star Jay Leno hosted the launch party, rock icons the Rolling Stones provided a theme song (for a reported $8 million), and computer stores around the country stayed open until midnight so eager techies could be the first on their block to try the new operating system.

The launch this week of Windows Server 2003, the first mass-market 64-bit operating system, is more low key. But it may prove to be a similar watershed event for the industry. Business-technology managers who don't want to pay premium prices for 64-bit RISC systems running Unix now have a lower-cost alternative. The 64-bit Enterprise and Datacenter editions of Windows Server 2003 provide more power and speed than 32-bit versions, run on Intel's Itanium chips, host 64-bit applications from Microsoft and key enterprise software vendors, and are priced at $999 and $3,999, respectively--the same as 32-bit versions of the operating system.

It sure took long enough to get here. Intel and Hewlett-Packard have been developing the 64-bit Itanium chip architecture since the early '90s, and a developers' edition of 64-bit Windows has been available for nearly two years. At last, all the pieces are coming together: Microsoft this week also will unveil a 64-bit version of its SQL Server 2000 database, and there will be databases from IBM and Oracle; apps from i2 Technologies, J.D. Edwards, SAP, and SAS Institute; and systems-management software from Computer Associates, HP, and Symantec tuned to run on the new systems. HP, NEC, and Unisys plan to ship Windows-on-Itanium systems this summer or earlier, and IBM will enter the market by midyear.

Windows Server 2003 changes the conventional wisdom of the computer industry, says Roger Jones, CIO of Fortis Health, the health-insurance division of Fortis N.V., which plans to run Windows Server 2003 on part of its new high-end Unisys system this month. "A decade ago, if you had an office with 10 people, you would use Windows," he says. "To support 10,000 people, you'd buy Unix, and to support 20,000 people, you'd buy a mainframe."

Not any more. As part of a cost-cutting plan, Fortis Health is replacing 17 RISC servers. It expects to slash application costs by 40% by turning data analysis, file serving, and Citrix thin-client support over to Windows Server 2003 Datacenter Edition running on eight Itanium 2 chips inside a 32-processor Unisys system. "Sixty-four-bit Wintel raises the bar for what you can do in Windows," Jones says.

Computers running test versions of 64-bit Windows and SQL Server have snared three of the top 10 spots on the Transaction Processing Council's closely watched list of business-workload benchmark results for a single system. The second-fastest machine on the list, a $5.6 million NEC system with 32 Itanium 2 processors running Windows Server 2003, crunches transactions just 5% slower than the top-rated system, a $12 million Solaris-on-Sparc Fujitsu machine with 128 CPUs. "This is Microsoft going back to its original playbook and being the cost leader," says David Freund, an analyst at research firm Illuminata.

Sixty-four-bit Windows Server 2003 will appeal to users who've run out of headroom on 32-bit Windows systems, which address only 4 Gbytes of memory directly, making it hard to hold large databases in memory--crucial for handling hundreds of thousands of transactions per minute. A computer that processes data 64 bits at a time can address up to 1 petabyte of data. That makes it a candidate for big databases and server-consolidation projects.

Among the first Windows 64-bit servers will be Unisys' ES 7000/560, which can support up to 32 Itanium 2 chips and 106 CPUs overall, and HP's Superdome server, with up to 64 CPUs and 512 Gbytes of RAM, both due this summer. NEC next week will debut 64-bit Windows 2003 Enterprise and Datacenter editions on eight- and 16-CPU models, as well as the 64-bit Datacenter Edition on a machine with up to 32 CPUs and 512 Gbytes of RAM.