WD easystore 4TB External USB 3.0 Hard Drive Black WDBCKA0040HBK-NESN - Best Buy. This 4 Terabyte Hard Drive has enough space to back up the entire U.S. Space program. That means it has enough room for a few hundred images of your data, if not more. Just plug it in, and run your imaging software. A hundred bucks for peace of mind. If you don't do this, you are insane. Back up your data now, today. Do it at least once a week. Enough said.