A new bootable scanner from Microsoft has recently become available. Probably using the Security Essentials/Forefront signatures for detection. Looks like it could be a useful addition to clean infected computers.
p.s. If you put it on a USB it asks you to format the stick first (so obviously you lose everything) but you can then update the definitions when you use it.
Matty
Indeed, this sort of thing is always useful… despite it probably being MSE signature based. Thanks Matty. :-TU
Now if we can just convince Comodo to release something like this. 
Interesting.
It has been promised by Melih but haven’t heard about it for a while.
The great of the tool is the ability to boot an infected (unbootable) computer.
Hope people can test in real infected systems and post back if it really reverts the changes and allow booting. Seems promising for cleaning computers.