Windows Defender Offline Beta

[green granite]

This looks as though it might be very useful, as it runs as a independent boot-able program from a cd/mem stick:

Windows Defender Offline Beta

What is Windows Defender Offline Beta? (http://windows.microsoft.com/en-US/windows/what-is-windows-defender-offline)

[Loose rivets]

Interesting indeed.

Does one have to have a stick that's clean. i.e. having some kind of HD-like boot sectors free at the front end?

no, I have no idea how an OS sees a stick.

Can one easily cause the download to go straight to the chosen media, or will it have to be copied from a potentially infected HD?

[green granite]

It installs directly onto the chosen media.