Hardware requirements for Microsoft operating systems have grown exponentially since the days of DOS, with its necessary 8086 processor and 64KB of RAM. So, with Windows XP Service Pack 2 and possibly "Windows XP Reloaded" on the way, and Longhorn looming in the background, should businesses anticpate more monumental hardware upgrades?

The answer is complex, partly because Longhorn is fading further and further away into the misty future - some pessimists putting its arrival at 2007 or even 2008 - and because the old patterns of hardware and software upgrades are fading away. Longhorn promises new technologies such as the WinFS file system, based on relational database technology, and a DirectX-based user interface filled with 32-bit elements, all of which will consume plenty of resources.

A rumoured "average" hardware specification for a Longhorn PC circulating on the Internet features a dual-core, 4GHz to 6GHz CPU, minimum 2GB of RAM, up to a terabyte of storage, built-in gigabit Ethernet, 802.11g wireless and a graphics processor running three times faster than those currently on the market. Microsoft was expected to announce these specs at its recent developer conference, WinHEC, but, given Longhorn's ongoing delays, says it has opted to chat in private with hardware makers; the company told Techworld that these specs are more likely for a "performance" than an "average" system. Still, in two or three years' time, such a system could be far from rare, said analysts.

Windows' hardware history
First, a quick look back at Windows' hardware history. In retrospect, the two really big leaps were from DOS to Windows 3.1, the first Windows version that gained any sort of popularity, and then the jump to Windows 95, which introduced Microsoft's first true graphical user interface. In 1995, a Windows 95 purchase almost certainly meant a new PC for most. Since around Windows 98, however, hardware's capabilities have accelerated more quickly than the operating system's demands, say analysts, so that a PC bought in order to run Windows 2000 could usually be upgraded to Windows XP.

By the time Longhorn arrives, few expect that it will make serious demands on the hardware of the day, no matter how much of a resource hog it is. "I think the hardware will still be well ahead of the software by the time Longhorn comes out... unless it's unbelievably badly written," says IDC analyst Roger Kay.

From DOS' 8086 processor and 64KB of RAM, many users needed a new PC to cope with Windows 3.1, with its demand for a minimum of a 80386 chip and 2MB of RAM. With some new PCs housing 486s by then, that wasn't too hard to achieve. Business-oriented NT 3.5.1 had somewhat steeper requirements: an 80386 chip and 16MB of RAM.

Windows 95's basic system requirements were a 386DX chip, 4MB of RAM, a 50-55MB hard disk, a 3.5 inch floppy disk drive and a VGA-resolution monitor; note, the CD-ROM drive was seen as a luxurious extra. In practice, Microsoft's minimum system requirements were too low; the recommended system used a 486 processor, 8MB of RAM and a 256-colour SVGA monitor.

Three years later, Windows 98 needed another significant step up, a basic system needing a 66MHz 486DX2 processor, 16MB of RAM, 225MB free hard disk space and a CD-ROM drive. Windows ME (Millennium Edition) wasn't intended for business use, which was just as well because it was considered a technical disaster, causing endless system crashes. It was the last release to use the 9x kernel, and was intended to fill in the long gap between Windows 98 and Windows XP, once XP had been delayed - rather like the contemplated "XP Reloaded". Microsoft's basic ME system specification called for a 150MHz processor, 32MB of RAM, 320MB of hard disk space, a modem and even a sound card.

Back on the business side, Windows NT 5.0 - later renamed Windows 2000 - needed a 133MHz Pentium-compatible CPU and 64MB of RAM, as well as a 2GB hard disk with 650MB of free space. Windows XP brought the consumer and professional Windows releases together, based on the Windows 2000 code base. An XP machine can limp along with the minimum requirements of a 233MHz Pentium-compatible CPU and 64MB of RAM, but Microsoft recommends a 300MHz or faster Pentium II, 128MB of RAM, 2GB of disk space, a 12x CD-ROM drive and a Super VGA monitor. In practice, the more memory you throw at an XP-based PC, up to about 512MB, the faster it runs.

A 'good enough' Windows?
As Microsoft's technology has become more usable and more stable, demand for an ever-better Windows has faded, industry observers say. Moving from DOS to Windows 3.1 added graphics; moving to Windows 95 made the operating system much easier to use; upgrading to Windows 98 or Windows 2000 significantly increased stability. The jump from Windows 2000 to Windows XP is less compelling, say analysts, and businesses evidently think so too, since they have not rushed to upgrade in the three years since XP's release.

"There is definitely a plateau where people are fairly happy with what they've got," says RedMonk principal analyst James Governor. "'Good enough' computing is something Microsoft brought to the industry, and it is now putting pressure on them." When a Microsoft executive pooh-poohed StarOffice by remarking it was on the level of Office 98, he unwittingly put his finger on a serious dilemma for Microsoft - namely that Office 98 is all most people need, Governor notes.

Microsoft's line is that its operating system must keep pace with the development of technology. "The exponential increase rate of hardware performance... necessitates an increase in operating system performance to ensure that buyers of new equipment get the most value from their investment," says Windows Client product manager Paul Randle. But the reality is that business upgrades are rarely driven by fancy new hardware or software nowadays, say analysts - they are driven by the availability of technical support.

This is why it is so controversial when Microsoft cuts off support for an older operating system, and lies behind Microsoft's drive to get customers onto its subscription-style "Software Assurance" programme. "The three-year upgrade cycle for hardware is apparently not supportable, and it's not how enterprises want to, or are, investing in technology," says Governor. IDC's Chris Ingle agrees. "Microsoft is moving from a standard upgrade cycle to getting customers to see all its products as a coherent whole," he says. "They are pushing more server products and subscription products. Desktop upgrades don't figure very highly on the list of priorities for businesses."

Marketing not technology
At WinHEC, Microsoft revealed its next big business opportunity on the desktop: not a flashy new Windows release taking advantage of the technological developments of the past three years, but a marketing campaign in the second half of this year, aimed at getting Windows 9x users to upgrade to Windows XP.

The potential market is huge: Microsoft estimates that users of Windows 98 and older operating systems make up more than half the PCs in use. Among businesses, 80 percent of companies still run some machines on Windows 95 or 98, according to a December study from technology consultant AssetMetrix. Those firms that do include 9x machines had an average of 39 percent of their desktops running 95 or 98, the research firm says. Only a fraction of these machines would be capable of running Windows XP, meaning new PCs would be needed for most.

The Windows marketing push, Microsoft's first since XP's launch, shows where the future of hardware upgrades will lie, say analysts. "The disappointing adoption of XP means there is plenty of room for growth," says analyst Governor. "The challenge for Microsoft is finding the right narratives to persuade customers to buy, and making sure people don't migrate to other platforms, like Linux."