Complex sentence: He went on to become president and CEO of Symantec, guiding it into the software utility and anti-virus businesses until he left in 1999 to become president and CEO of Oblix, a silicon valley startup that creates software for web security.
Split into simpler sentences: He went on to become president and CEO of Symantec, guiding it into the software utility and anti-virus business. He left in 1999 to become president and CEO of Oblix, a silicon valley startup that creates software for web security.