1TB hard drive for mac with no power supply?

I got a Western Digital Elements SE 1TB portable hard drive on Black Friday. It runs on USB 2.0 power. It comes pre-formatted for Windows, but the box says it can be reformatted for Mac, among others. So presumably most of the portable hard drives which get their power from USB would work.

I have been asked such a question quite a few times in the past.
Generally any hard drive should work with a mac. External or Internal.
If a hard drive doesn't say mac compatible will it "not" work in a Mac? No, but a mac certified product will have done more testing to provide a product produced flawlessly to work with Mac.