Diane Greene

As the No. 3 executive at Microsoft, Paul Maritz presided over the company's Windows juggernaut, turned aside threats from Netscape and Sun Microsystems, and pressed the company to embrace the Internet. Now, the longtime software executive is looking down Microsoft's barrel from the other end, trying to help his new employer, VMware, triumph where past Microsoft competitors fell short.

VMware Inc. abruptly replaced co-founder Diane Greene as chief executive Tuesday and lowered its sales outlook, triggering alarms that pounded the business software maker's shares to their lowest depths since the company's lucrative public offering 11 months ago.

Former Microsoft Corp. executive Paul Maritz took over as VMware's new leader. In the past few months, Maritz had been running a division of VMware's controlling shareholder, data storage specialist EMC Corp.