removing malware from clean computer

All the malware approaches I have come across assume you are removing malware from an already affected system i.e. malware is active on the machine you are removing it from. I believe this is what requires the need for "manual" removal of some infections--you need to change some files that your operating system has active/open.

I would think that the most effective way to remove malware would be to remove the harddrive from the impacted system, attach it via a usb adapter to a "clean" machine and run the anti-malware software from the clean machine--you would be able to do anything to the attached drive without impacting the operating system of the clean machine.

Are there any anti-malware applications that support this approach? Are there any drawbacks to this approach? Does this remove the need to do manual malware removal?

Much thanks in advance
David