Calling XP Service Pack 2 a new version of Windows XP may be exaggerating a little, but it's certainly much more than the average collection of patches we're used to seeing.

This 264MB monster (or 100MB if you install it via Windows Update) not only fixes bugs in the OS, but also adds brand new functionality both to core services and applications such as Internet Explorer and Outlook Express.

We've been using the beta Release Candidate 2 (RC2) for some time, and generally we're impressed. It seems pretty stable and has not yet created any major problems with the PCs we've installed it on. All the screenshots here were taken using build 2156 of RC2, so it's possible that some details may be changed by the time of the final public release version.

Microsoft's focus with SP2 is security, security and security - many of the changes are deep in the inner workings of XP and won't immediately be obvious to users. They could cause some problems for existing applications, so as ever it's wise to do a full system backup before installation.

In this overview we've concentrated on giving you a visual tour of the major new features - the technical changes are covered in great depth on the Microsoft website if you're interested. We plan to do a more in-depth look at the underlying technology in a future issue.

There are a couple of features not illustrated here, such as the addition of plain text email formatting to Outlook Express, but we've tried to cover as many of them as possible within the available space. The behaviour of Internet Explorer has also been changed, for example, to prevent malicious websites hiding the navigation bar or spawning multiple pop-ups. Overall we believe SP2 is a genuinely worthwhile update - many of the features are well overdue, but 'better late than never' is a phrase that's becoming familiar to most Windows users.

Click on thumbnails for a larger image.

Service Pack 2 is at least a 100MB download. Before you download it you'll be prompted to install the new Background Intelligent Transfer Service (BITS), which speeds up future patch downloads by only downloading files that have changed.

After installation, the first thing you'll see is the new Security Centre that gives you easy access to your firewall, automatic updates and Internet settings. The antivirus settings can't be changed from here, though. Security Center can be opened from Control Panel.

If the publisher of an executable program can't be determined, Windows will now warn you before it lets you run it. This feature checks whether the program has a digital signature, something that many valid programs don't have at the moment. It's another welcome security feature in SP2.

Bluetooth users will be very happy to see this screen. Service Pack 2 adds native support for Bluetooth - this screen shows the Options tab found when you double-click the new Bluetooth applet in Control Panel. We found it worked well using an unbranded USB Bluetooth dongle, with drivers being found automatically. The control panel lets you configure discovery settings and connections to other Bluetooth devices. You can also set up Bluetooth COM ports.

Adding a Bluetooth device is made simple with the new Add Bluetooth Device wizard. SP2 also adds support for six standard Bluetooth profiles including Personal Area Networking and Dial-up Networking.

As well as providing access to the new Security Center, icons for the Firewall, Automatic Updates, Bluetooth and a new Wireless Network wizard have been added to the Windows Control Panel.

If the firewall detects a program trying to accept incoming network traffic, you'll get this dialogue box that lets you block or unblock programs.

The new Windows Firewall (which is an IPv6 firewall) is enabled on all network connections by default. You can add exceptions to allow individual programs to accept incoming Internet traffic. The firewall uses stateful packet inspection to determine whether network traffic is allowed or blocked: if an incoming network packet has not specifically been asked for by a program on the Exceptions list, it will be blocked.

In the past, administration of the firewall for multiple network connections was far too complicated. Now you can control the firewalls on each of your network connections from a single tab in the firewall configuration screen. Each network connection can have its own separate settings and Exceptions list, so for example your dialup connection can be configured more securely than a local peer-to-peer Firewire connection.

The Automatic Updates control has had a visual makeover, but the only new functionality is the ability to unhide updates you've chosen to hide on the Windows Update site. This 'hide' feature is new for the Windows Update version 5 website and is useful for reducing visual clutter. Microsoft plans to eventually offer Office updates via Windows Update.

At long last Microsoft has added a pop-up blocker to Internet Explorer. You can customise its behaviour, and a small Information Bar appears in the browser (below the toolbar) when something is blocked. It also blocks any automatic file downloads not initiated by a mouse click, but clicking on the Information Bar lets you temporarily override this behaviour.

It's easier to control and monitor Browser Helper Objects (BHOs) that have been installed in your browser, courtesy of the Internet Explorer Add-on Manager. This should help prevent malicious controls taking over your browser.

The Wireless Network Setup wizard greatly simplifies the setup of a wireless network in XP. You can also save your network settings to a USB Flash drive, making it much easier to add and configure new wireless clients.

If you use an AMD Athlon 64 or Opteron processor, or an Intel Itanium, Windows can take advantage of their hardware Data Execution Protection features. This is a hardware capability that can lock areas of memory to prevent exceutable code running in those areas. It's intended to prevent certain types of virus behaviour whereby a virus takes over memory areas belonging to valid programs and runs malicious code instead. As you can see from the screen, our Intel Pentium 4 doesn't support this feature.

You can now let Windows Update automatically search for device drivers when you add a new piece of hardware, a boon for older devices.