Microsoft has released a new beta tool called Windows Defender Offline that's designed to scan for spyware and viruses prior to Windows startup, which could make it effective against malicious software, like rootkits, that can be difficult to remove while the OS is running. It's designed to boot from removable media such as a CD, DVD, or USB flash drive, making it particularly useful for troubleshooting multiple computers. The tool has similar functionality as the new version of Windows Defender that will be integrated with Windows 8, which adds the virus protection that's not included in the version that ships with Windows Vista and Windows 7. Windows Defender Offline beta is now available for download as a 214MB setup file from the Microsoft website.