No one expects sparks to fly when Microsoft chairman Bill Gates and Apple's CEO Steve Jobs appear on stage together later this week. But it's clear there's no love lost between the two camps.

Apple's clever series of "I'm a Mac, and I'm a PC" ads have needled Microsoft, portraying the software giant's products as awkward and unhip.

While the overwhelming majority of desktop and laptops still use Microsoft operating systems, sales of Apple Mac computers have been on the up and up over the past year on the back of growing ennui over Windows.