If you read the letter (http://www.vectronicsappleworld.com/macintosh/memo.html http://www.vectronicsappleworld.com/macintosh/memo.html), Gates's advice was to

If you read the letter (http://www.vectronicsappleworld.com/macintosh/memo.html http://www.vectronicsappleworld.com/macintosh/memo.html), Gates's advice was to license Mac hardware technology to OEMs, enabling a "Mac-compatible" hardware market in which licensing the Mac OS would be feasible. It is easy to forget that in 1985, the modern assumption that all computers are identical Intel-specified x86 boxes was not yet in place.