So, if I want to wipe my HD completely clean and re-install Lion...how do I do this?

[Amnesiac7]

I have a portable HD, so I do want to back everything up first, but I'd like to have my HD completely empty.

Since I downloaded Lion, like everyone else, through the App Store... what do I do?

 

[Intell]

Use the Internet Recovery option. Use a search engine for more information about Internet Recovery.