John Hodgman as PC and Justin Long as Mac.
The Get a Mac campaign was a television advertising campaign created for Apple by TBWA\Media Arts Lab, the company's advertising agency, that ran from 2006 to 2009. If you have 37:35 minutes to spare, check out the complete collection of "Get a Mac" ads and for some history, follow up with the Wikipedia page.
Which one was your favorite? Post it in the comments below.