I assume that you already downloaded and installed the WAIK for Windows 7 and the Microsoft Safety Scanner.

Of course, you can also create a boot CD with Windows PE and Microsoft Safety Scanner. The advantage of the Windows PE solution is that you can add Microsoft Safety Scanner to your Windows administration toolbox on your USB stick.

Many antivirus software vendors offer boot kits with their scan engines, which are usually based on Linux. Windows PE is a good choice for an offline antivirus scan because the operating system is lightweight and boots up quickly. Sophisticated viruses are difficult, and sometimes impossible to remove while Windows is running and the best way to remove them is to access the infected drive from a second OS while Windows is offline. The fact that the Microsoft Safety Scanner runs on Windows PE makes the free antivirus tool much more useful because it allows you to scan a Windows installation while it is offline. Microsoft Safety Scanner as offline antivirus tool on Windows PE 3.0

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