It's not just users that have lower privileges than in Windows XP, some applications such as Internet Explorer 7 run as limited users, with little or no ability to make changes to your system or install unwanted programs. This has led to perhaps the most criticised feature of Vista: User Account Control (UAC).

Any time you need to do something that requires administrator privileges - even if you're running as an administrator - Windows pops up a dialog box that asks for permission to complete the action. If you're running as a standard user you'll need to enter an administrator password. In early versions of Vista UAC was both persistent and a regular visitor, stealing focus from running applications.

It's still there in the final version, but now it's a lot less intrusive. Instead of stealing focus, UAC calls for attention in the task bar, letting you finish what you're doing first. Once you've finished configuring a PC and installing software you'll hardly see the UAC dialog at all, and it shouldn't be part of your day-to-day Vista experience.

Microsoft makes it clear when you're going to see a UAC dialog: look for a little shield on an icon or in a menu. Hardware choices Vista's performance is nothing to complain about; it's mostly similar to Windows XP on the same hardware.

You'll want more than the 512MB that XP requires to operate smoothly; with 1GB of RAM Vista is speedy and responsive, and if you plug in a flashdrives that is fast enough to use for ReadyBoost you'll notice extra speed - and a little extra battery life on portables. And with Windows Defender watching for spyware and taking care of automatic disk defragmentation, you shouldn't find performance degrading substantially over time.

Once you get used to integrated search in the Start menu, you may fi nd you gain some speed by getting to what you want faster too. Apart from memory and a reasonably modern processor - a PC you've bought in the last three years will have no problems - what really matters is your graphics card, because that determines whether you can run all the Aero features such as transparency with Glass, Flip 3D and live taskbar thumbnails.

Even some integrated graphics can run Aero, depending on the memory and DirectX 9 support; you need either 128MB of graphics memory or shared memory and 1GB of PC memory. Nvidia has written a driver that allows some graphics cards to switch to shared memory to support Aero, which means more laptops will give you the full Vista experience.

Startup speed is dependent on your system and connected devices; dropping the graphical boot screen saves a few seconds but we'll need to wait for devices with Vista logos to see if Microsoft can push hardware manufacturers to deliver faster boot times.

But as Vista runs well on many existing systems, that's where we recommend you use it to start with. Buying a new PC is one way to get Vista; you'll get either a voucher for a free or cheap upgrade, or Vista preinstalled with most new systems. But unless you were planning on a new system, or your kit won't cope with Vista even if you add a gigabyte of memory and a new graphics card, we wouldn't suggest buying a new PC just to get Vista.

Wait for six months to a year for hardware that makes the most of Vista such as hybrid hard drives, notebooks with integrated flash ReadyBoost cache and Sideshow-enabled devices such as keyboards and Media Center remote controls. That way you'll also get a quad core CPU in a desktop and 802.11n on a laptop.

The business version has all the networking features plus full image-based backup. As youd expect from a workhorse there are no home entertainment features, no parental controls, but oddly, no BitLocker either. That's penny pinching, as data on notebooks and tablets is exactly what needs protecting. Simon Bisson and Mary Branscombe