how do you know if a hacker hacked in your computer?

[Jason]

Bingo! thats right. Win98 has no built in protection, its like driving around with a Ford Pinto, a full tank of Gas, and having a bumper sticker that says "Please tailgate me".

The moral of this lesson is:
By the time you stop to check for someone hacking you (the possiblity of which is very small unless you have something they want and are on broadband) its already taken place.