Many thanks for your replies people, they've helped greatly. However I am concerned that the use of these two accounts is not only badly documented by M$, but the accounts themselves are hidden. The only detail I've found on M$'s website is a techy doc on technet about the issuing of tickets to allow remote assistance to work - not something the average user will read. As these two accounts are designed specifically for remote access to your machine, they must be susceptible to abuse and hence the user community must be made more aware of them and how to control them.