I need to move Gmail conversations to hard/flash/dvd drive for an investment scam (no, it's not Ugandan) investigation and prosecution... How to do this?
Scott Hanselman wrote an article about this. There is a tool which helps make backup of your Gmail emails. Although he is talking about automatic task, you can get the idea from his article Automatically Backup your Gmail account on a schedule with GMVault and Windows Task Scheduler
The tool is called GMVault and you can download it at http://gmvault.org/. It's pretty straightforward to use it.
Checkout Beyond Inbox, which helps make backup of your Gmail emails to hard drive or any other account too. It runs on all the OS including Windows, Linux and Mac.
Download Beyond Inbox from here : http://www.beyondinbox.com/beyondinbox-download.html