VMwareOnce upon a time, PCs were PCs, Macs were Macs, and these machines lived on your desk. Now Windows can run on a Mac, and Mac operating systems on a PC. Moreover, your desktop can be hosted on some server somewhere. Such "virtualization" is a big deal - and at its forefront are Diane Greene and VMware. She cofounded the company in 1998 with her husband, a Stanford engineering professor. (Earlier gigs include designing oil rigs and windsurfing gear.) VMware has $709 million in revenue and is sailing toward an IPO. --O.R.