Why do you want to spy on your teenage son/daughter.
it depends. do they know how to run a spyware scan? because if they do, then they will catch it because any spying software will come up as spyware. but if they don't chances are that they wouldn't know how to clear the history of the cookies on their computer, and you could just look through those. But if they do, you would want something that you connect inline with the keyboard connection, that will store all keystrokes, and you hit a specific combination to recall them
ok ok back on subject you said your company is not big enough to have an I.T department IMO comapnies should not issue staff with computers without having some kind of dedicated team / person to look after them even if it as an external company that you call in once a week
and do you own / run the company ? if not then once again its not really your fault if customer info gets stolen was you told if u ever leave your comuter to lock it ?
these are basic things that people should be told before being allowed to use a company computer for safety reasons even if it is really stupid stuff like never give out your password there should always be a brief before being allowed on a company pc so:
if u are an employee who did not recieve a 'computer policy brief' then you are not responsible.
if your are the owner / manager of the company and did not enforce this on your employees or do this basic stuff yourself then it was quiet foolish.
if you are an employee who recieved a 'compuer policy brief' and you did not obay this then that was kinda foolish again..
sorry but again i dont see y u think some1 has a keylogger on your pc ?