Home users are offered a choice of two Vistas

Every day around the world 800m people use the Windows operating system �C at least half of them at home or in their personal lives.

Now the company is betting it can persuade most of those home users to upgrade to the one of two versions of its new Windows Vista operating system designed specifically for consumers �C Windows Vista Home Basic and Windows Vista Home Premium. (Another version called Vista Ultimate combines features of both the home premium and business versions.)

I have been running various beta test versions of Vista Home Ultimate for almost a year now and although I have yet to test the final code, I think consumers will be find plenty of reasons to justify upgrading to Vista, or buying a new PC with it already installed.

Among them are improved security, integrated search capabilities, better communications and multimedia options and, of course, the sleek Aero interface with its see-through windows.

Before installing Vista on an existing machine, consumers can go online and download an Upgrade Advisor which will test the current hardware and determine which version of Vista is best suited for them. Microsoft even suggests it makes sense to run the Advisor now to see if it would make sense to buy new hardware this holiday season.

Installing Vista is fairly straightforward and mostly automated. It takes about an hour, provided there are no hiccups. After installion, prompts appear for a series of customisable settings including username and password.

At the end, Vista checks the PC and grades it on a five-point scale. When Vista fires up for the first time, users are greeted by a Welcome Center that includes tools to migrate data from another hard drive partition or physical hard drive, various services offered by Microsoft and the new "Sidebar" preloaded with three so-called "Gadgets" �C a clock, a photo gallery slide show, and an RSS (real simple syndications) news feed.

Among the immediately noticeable changes, Vista home users will see a new round "Start" menu button designed to make it easier to find and launch applications, music, photos, e-mail and Internet Explorer favourites.

Vista Home Premium users will also no doubt be struck by the Aero interface with its stunning visual effects such as translucent glass-like window borders that enable users to see behind application windows and "Flip 3D" that enables users to flip through all the open windows.

The new Aero graphics engine is dynamic, so file icons not only show you the contents of the file but also scale to the size of the page.

And now users can view thumbnails of open tasks across the bottom of the screen. These, too, are dynamic: you could, for example, monitor the progress of a sporting event by passing your mouse over the open application.

Mike Sievert, vice-president of Windows client marketing, says the underlying concept behind Vista comes down to four things: easer to use, safer, better connected, and more entertaining.

"Windows Vista makes everything easier. It makes finding and using and sharing information easier," he says. "People don't have to think about their computer, they can just enjoy these experiences. They can be productive.

"When people get their first look at Windows Vista, one of the things they notice right away is the visual fidelity of the system.

"And that, combined with another phenomenon, which is the ubiquity of search, search being integrated everywhere in the new operating system's user interface, so that things are always at people's fingertips, and I'm talking about everything, not just their documents, maybe it's their programs."

Search is what Mr Sievert calls "contextually relevant" in Windows Vista, which means that if, for example a user types "mouse" with the control panel open, up pop the setting for the mouse.

"But it's also about making it safer," says Mr Sievert. "It's important that people's treasured data, their family memories are protected, that their children are protected from content that's not appropriate, that their systems are protected from malware.

"Since we first conceived Vista some years ago, it's always been about this, what we call the operating system fundamentals, making people's digital world safer."

Vista has also been designed to make it easier to connect laptops to other networks, and to make using a PC more entertaining and enjoyable.

So, for example, the new Windows Photo Gallery allows users to collect all their pictures, tag them with useful information so that they can be searched and found more easily, organised more easily throughout the system, edited and fixed �C all the time preserving the original.

So which version of Vista should you choose?

Windows Vista Basic, which has been designed primarily for older hardware, includes the new file search capabilities and parental controls, with a lot of extra media functions.

All consumer versions of Windows Vista will include Windows Sidebar, Windows Media Player 11, Windows Photo Gallery, Windows Movie Maker, Windows Firewall, Windows Defender antispyware, Parental Controls, Internet Explorer 7, Windows Mail, Windows Calendar and a new Games Explorer.

Most consumers however will probably purchase the Windows Vista Home Premium edition, which offers in addition Windows Gadgets, Windows Vista Media Center, and Windows Tablet PC (including handwriting support), along with the native ability to author and burn DVDs.

What sort of hardware will consumers need to run Vista and should consumers buy new PCs now, or wait until Vista is launched?

Most modern PC hardware will be able to run Windows Vista and many recently acquired machines already carry a "Certified for Windows Vista" sticker.

But even newer hardware is likely to carry one of two new stickers �C "Windows Vista Capable", or "Windows Vista Premium Ready". Microsoft says 98 per cent of the PCs now on store shelves are Windows Vista capable.

Typically, Vista capable machines will have a minimum of 512MB of memory, a reasonably powerful processor and good graphics capabilities. But as with previous hardware specifications, this should be treated as a minimum �C I would recommend at least 1GB of memory.

If you want to be certain of being able to run rich 3D applications and experience the full features of the Aero interface, including translucent glass windows, pick a machine that is Windows Vista Premium ready, as it requires more sophisticated graphics capabilities.

Alternatively, purchase a Windows XP Media Center Edition or Windows XP Home PC that will allow you to upgrade to the Vista Home Premium Edition at a discounted price.

For all that is new in Vista, there are also some features that are missing, including a new file storage system that Microsoft abandoned early on in the development process when what became Vista was codenamed "Longhorn".

"Vista really is three stories in one release cycle, and the one we learned the most from is actually the one that's farthest ago in time," said Steve Ballmer, Microsoft's chief executive at a recent industry summit.

"When we finished Windows XP, we started on something, and I'll call it 'Longhorn' to distinguish it from Vista.

"It was the first thing we worked on. And we were really trying to re-engineer all major components of Windows and get them all to rely on each other and integrate with each other.

"There was too much new invention going on simultaneously with integration, and that was really beyond the state of the art for us or frankly for anybody else in terms of engineering complexity.

"We learned that we have to innovate and integrate, not necessarily try to do both at the same time, because it just creates chaos in the engineering process."

Vista may be a little late arriving, but in the end, most consumers will probably decide the wait was worthwhile.