I've used pretty much every anti-virus/anti-malware product on the market over the years and although they all have their different strengths and weaknesses they all have one common vulnerability - rootkit detection. How can you be sure that your av software has really cleaned your PC when the host operating system has been compromised at the lowest possible level? You can't. Even the mighty ComboFix and GMER (Google it noob) have failed to clean some rootkits that I've come across, leaving me to fart around with re-writing boot sectors and other manual grief that I can't be bothered with. A few people make offline scanners (McAfee, Symantec etc) but they generally need you to mess about creating a boot environment (using Windows PE or some such).
Came across Windows Defender Offline yesterday and have tried it on a few test machines that I had infected with various nasties. Looks like a great piece of software and will now be one of the primary tools in my arsenal against malware.
Here's the link, in Beta at the moment and comes in x32 and x64 flavours (dependant upon the version of Windows installed not your hardware), can be burned to CD or you can make a bootable USB stick (which is updateable via the setup software) straight from the downloader. Very easy to use and quick.
http://windows.microsoft.com/en-US/windows/what-is-windows-defender-offline
