Microsoft has released a new security tool for Windows PCs called Windows Defender Offline Tool which you can use to scan you computer for malware before Windows even boots.
Windows Defender Offline is currently in beta, and you can download the installer for free. You’ll then use that utility to set up a bootable CD, DVD, or USB flash drive so that you can run Windows Defender without booting Windows. You’ll need a device with at least 250MB of free space.
Since the tool lets you scan your computer for spyware or viruses without actually running Windows, it may be able to identify or repair problems that are tougher to deal with on a running computer. It may also be able to help if you’re worried about using your computer while it may be infected.
Once you’ve created a bootable device with Windows Defender Offline, it should have the latest virus and spyware definitions, which is why you can use it without an internet connection. But from time to time you can run the installer again to download updates.
via Paul Thurrott