Microsoft have released a beta of Windows Defender Offline beta here – http://windows.microsoft.com/en-US/windows/what-is-windows-defender-offline
What is it? It is a bootable, offline anti-virus, anti-malware, rootkit scanner and removal kit. Just download and burn the ISO on to a bootable ISO or CD, and then boot your PC with the created media to scan, detect and remove any malicious code. You can read this post for instructions on how to create the bootable media – http://blog.powerbiz.net.au/online-tools/creating-a-multiboot-usb-drive-from-isos/