need rootkit remover to run on usb to sys drive

There are many rootkit scanning tools; however scanning while not booting the infected OS quite often misses many of these infections or at least may miss the active components of the infection because they will not be active. When you boot from another OS, you don't have the any aspects of the infection that are in the registry visible because you are not loading that registry.

However if you wish to experiment with some scans, your can find many in the below download folder. Just search of the keyword "rootkit"

http://www.majorgeeks.com/downloads31.html

Also something else that you need to be very careful of. When you do not boot from the infected system, all files, folders, registry hives,...etc on the infected drive are not considered to be protected system files since they are not part of the Windows OS you are currently booting from. Thus you could removed something that can cause the PC to become unbootable when you move it back to the laptop. So cleaning things this way should be a last resort and more often than not, removing a drive is not necessary.