The company owns the computer, and the network it is on, so nothing done in a
work environment is private. Most company's have you go through a 'training'
event and have you sign something telling you that they can / will monitor.
Where I work they now send you an email once a year and you login to a server,
read the training, answer questions and it is all filed away, and each year
people get fired because they do things against policy. Do home stuff at home,
it's cheaper than a lost job..