Despite his role as chief executive at one of the most influential companies in the world, Steve Ballmer is relatively unknown outside the technology industry - having always been eclipsed in the public eye by one of his oldest friends, Bill Gates. But when Gates steps out of his Microsoft office for the last time today, leaving the company in the hands of his former college buddy, 52-year-old Ballmer will step out of his shadow. Given his bombastic style and imposing physique - he stands 6ft tall and carries the broad, bone-breaking stature of a retired American football player - it is unlikely that Ballmer will find trouble making his mark. He is well known for his boundless excitement - which often explodes dramatically - and retains an unquenchable enthusiasm for the software company he joined 28 years ago. The clearest insight into the mind of the 63rd richest man in the world is probably a single, minute-long piece of video which shows Ballmer on stage at an internal Microsoft event , skipping around like a dervish. He screams, yelps and caterwauls, before stopping to shout "I love this company!". His bizarre dancing - more pumped-up sports coach than corporate executive - is now as much part of his legend as his notoriously quick temper. Microsoft employees - who would talk only on condition of anonymity - describe how Ballmer can become excessively angry in meetings, the most famous example being when one member of staff, ...