Ultimately, therefore, the new features in SP3 don't really add up to a compelling argument for an upgrade. But what it does offer is a simple mechanism to apply those little hotfixes and patches that accrue over time - especially for those who prefer to disable Windows Automatic Update.

Finally, we did not note any software or hardware compatibility problems with SP3, though with the colossal scale of today's PC-related ecosystem we wouldn't be surprised to if the odd glitch appeared eventually.

Windows Vista SP1: the features

If SP3 is a low-key final fling for Windows XP, the first major service pack for Vista is a much, much bigger deal. Not only might it make or break Windows Vista, it could even have a major influence on the long term health of Microsoft itself.

Historic upgrades: as with all service packs, SP1 rolls up all hotfixes and patches to date. Obvious examples of patches that have already been made available via Windows Update include the Virtual Space management tweak which reduces the amount of memory used by games in Vista. Due to a quirk in the original Windows Vista Display Driver Model (WDDM), some games were pushing the 32-bit build of Vista towards its 2GB virtual address barrier. Once that limit is breached, be prepared for a blue-screen bomb out.

Performance improvements of the new-to-SP1 refinements, the most important are tweaks to the way Windows Vista handles file copying, management and transfers.

Microsoft has been quite open about the reasons why Vista can be painfully slow for certain types of file movements, particularly network transfers. The short version of an extremely complex explanation is that changes to the way file data is buffered during transfer in the original build of Windows Vista leads to increased disk or memory stick access and reads.

Also, there are differences in the way Windows XP and Windows Vista report when a file management task is completed. Windows XP will tell you the job is done when all the data has been copied to the write cache. Windows Vista is more of a stickler for the truth and will not give the all clear until all disk writing is completed.

For Windows Vista SP1, Microsoft has reinstated most of Windows XP's buffering procedures while keeping one or two of the Windoes Vista measures that improve performance for really big files.

UI enhancements: on the interface side, the only significant refinement involves a streamlining of User Account Control (UAC). By default - even for novice computer users - UAC can be a ghastly nag, constantly demanding permission to perform apparently innocuous procedures.

It's bad enough that many feel compelled to knock the whole thing on the head and opt to disable it, which rather defeats the object. SP1 reduces the number of security dialogue boxes in certain situations - for example, when creating new folders in protected locations.

General tweaks: beyond the headline-grabbing new features, there's a truly encyclopaedic list of detail enhancements. One good example is a partial resolution for the conflict between the MultiMediaClass Scheduler Service and the network stack.

In Windows Vista, the former has been given supremacy over the latter in terms of access to system resources in order to ensure that audio streams do not break up.

The downside to this is throttling of network throughput. It's really only an issue on super-fast gigabit networks, but for the record, Microsoft claims that the balance has been tipped back towards networking with compromising audio stream stability.

So, the enhancements that SP1 brings are as broad as they are deep. But is this bandage enough to stop Vista's bleeding out? In performance terms, we have to admit we were surprised at the proximity of Vista, be it the original RTM build or SP1, to Windows XP in the majority of our benchmark results. As far as gaming goes, time has no doubt healed some of the wounds.