Between the security improvements, the new interface and the major improvements for notebook users Windows Vista looks appealing, but are you going to feel happy about paying for it? You can add some of the underlying technology to Windows XP but there's no way to upgrade to the extra security.

Are the security improvements enough to switch for or is the rest of Vista enough to make the price tag - for the upgrade and for any hardware you'll need - feel like good value?

With so many versions, the answer is a mixed bag. So let's look at all the different features and versions to see whether you need to upgrade, whether you want to upgrade and what to pick if you do.

You only install Vista once on most PCs but the experience is still critical. Our test installations included upgrading from Vista RC1 and clean installations on a newly formatted hard disk.

Installing Vista

The update installation was, as expected, quite slow, and took nearly two hours. Microsoft spent a lot of the beta process investigating the update method and held install fests in the US to help track down upgrade issues. The result is a smoother update experience, with little in the way of problems.

You will need plenty of disk space free, as Vista's image-based install copies all the required files to your hard disk, before rebooting your system to start the installation. We would still recommend a clean install. For one thing, it's a lot quicker, and there's no worrying whether some legacy application or driver may stop your system from operating properly.

One key test of any new OS is application compatibility. Early versions of Vista had problems with some applications; but we found everything we installed on our test machines ran without problems. This included applications that crashed or failed to run even on Vista release candidates.

We didn't even have to adjust application compatibility - though some Internet applications needed to be given permission to cross Vista's built-in firewall, including Windows Easy Transfer for copying your files and application settings from another PC. Driver delays Microsoft has pulled the stops out on getting drivers certified in time for the final release. However many key drivers are still in beta, and we're unlikely to see final releases until the consumer release in January 2007.

Many Tablet PC owners won't find certified drivers. This is surprising, as Microsoft has made tablet functions part of the mainstream Vista platform. While most XP drivers will run under Vista, you'll need to check whether all your peripherals are compatible. We found most of the hardware in our test PCs was supported, including wireless networking.

This driver experience is considerably different from the launch of XP, when many older pieces of hardware were unsupported on day one. The 32-bit experience is a lot better than the 64-bit one though. Microsoft requires the use of signed drivers for any kernel mode, and many drivers have yet to be released.

Microsoft releasing the RTM code more than two months before the final consumer release gave them the time they need to get drivers ready, but early adopters should be prepared to upgrade drivers as they go.

Vista does take more advantage of the Microsoft update site than XP, and many drivers that aren't included on the install DVDs can be downloaded during the install, or upgraded after your first connection to the Internet. It's a good idea to keep any machine you're installing or upgrading Vista to connected to the network, as the installer will go online and download appropriate drivers from Windows update before starting the installation.

Vista performance can be increased by taking advantage of ReadyBoost. This uses a USB 2.0 fl ash drive to act as a disk cache. However it can't be just any flash drive - Microsoft requires a certain minimum performance, including a high random access speed. We found that most USB 2.0 drives we had didn't meet Vista's requirements.

Don't expect to just plug in a stick and see it working; you may need to try out several before you find one that works. Also, the larger the stick, the better the performance gain. We found that 1GB of fl ash or higher gave the most improvement.

User interface

Microsoft has used some of the time between the first release candidate and RTM to polish up "fit and finish". The Aero UI remains the same as before, though the available screen backdrops are tweaked, with the removal of some backdrops - leaving you with more scenic views and 'Vistas', but fewer of the other backdrop classifications.