Imagine how different the computing world would be if IBM had used proprietary chips in the original PC, rather than off-the-shelf components. The PC clone market would never have happened, and IBM, rather than Microsoft, might have emerged as the leading company of the computer revolution.

Or if Steve Jobs had never taken his fateful tour of Xerox PARC? Had he not seen PARC's GUI in action he might never have created the Macintosh. And then where would Windows be today?

In every industry there are key milestones that mark a change in the course of history, and the fast-moving technology field has more than its share. Presented here are 15 turning points that shaped the computing world as we know it today, including some that will continue to influence its direction for years to come.

Turning points 1-3
Apple's NeXT move | Dawn of Free Software | Microsoft dodges a bullet

Turning points 4-6
Handspring launches the smartphone era | That '70s spam | Rise of MS Office

Turning points 7-9
IBM's second coming | The ARPANet is for porn | The Web loses synch

Turning points 10-12
Linux staves off SCO | Intel dispels MHz myth | NetWare falls to Net

Turning points 13-15
IT made accountable | Apple flips chip strategy| Outsourcing goes global