A fancy yet amusing term. It basically means to defrag and delete a ton of files on your computer after you've accumulated a large sum of useless crappy files you no longer desire to have (or are getting in the way of important stuff).
Bob: Dude! My computer is running slow as shit! And I have so much crap on there I can't find half the files I need!
Joe: I think it's time you give your computer a digital enema.