Ever spent a couple of hours re-installing the OS on your desktop or laptop? An unplanned visit to a dodgy website is all it takes to give your OS that zombification feeling. However, Microsoft say that you'd be less likely to be reeled in to join a botnet army if you upgraded your OS to Vista. However, if you think your system has been 'botnetted', or if there's a patch failure or application compatibility problem that's causing you grief, Vista now has a tool enabling users to install a 'clean' image, replacing that currently running on their systems.

Most firms can re-install OSs by 're-imaging' their employees laptops – usually in minutes - once your 'trouble ticket' is next in line to be sorted. But what happens if your OS goes belly up at 5:01pm on Friday night? If you're running Business, Ultimate or Enterprise editions of Vista, you may have had the foresight to make an 'image' of the whole OS on a separate partition to the one on which your actual OS is running on.

On my test laptop Vista Ultimate's 'footprint', with no applications loaded, is nearly 8.5GB, but using the Vista's onboard Backup and Restore facility, available through the control panel, compresses this to 5.9GB and takes around 45 minutes for image creation.

To restore your system, you need to put your original install disk in, boot the system, choose 'Repair your computer', navigate to the 'System Recovery Options' screen and then pick 'Windows Complete PC Restore'. Then browse to the specific partition on your hard disk where the image is stored, select the image, cross your fingers and away you go. The time taken to restore my backup image was 20 minutes and even if your system has a lot of applications loaded, chances are it wouldn't take more than 45 minutes for you to be up and running again.

I normally use PowerQuest's V2i Protector, a package inherited by Symantec when they gobbled up PowerQuest in 2003. V2i Protector morphed into Live Recovery after the takeover, but it's still a neat program and protects most of my systems. V2i Protector allows different levels of compression and also allows you to do a baseline 'image' and then just do an incremental one, which saves a lot of disk space. A 7.4GB XP Professional image takes around 45 minutes to backup to a file size of 4.1GB and 15 minutes to restore.

It was the case that imaging a system meant that any malware on the hard drive was removed. However at the recent Black Hat security briefings earlier this year in the US, NGSSoftware's principal security consultant John Heasman, demoed techniques to secrete a rootkit inside PC device firmware. Imaging such a system would not get rid of the rootkit, but Heasman says that it's so easy to zombify user PCs that firmware rootkits are overkill. Let's hope he's right.