Sure you can.  Here's an example of the bad things that can happen...if
you accidentally shock your parallel port while you're changing it, that
30,000 or so volts can do horrible things.  Even more horrible if the
computer is on.  Of course, it isn't a guarantee that something bad will
happen, but the odds are higher.

Really all that it takes is a difference in potential from one device to
another and damage from a surge of power is possible.

Now, the question is how probable is the damage...not extremely, but
still, it never hurts to take precautions, especially one so easy as
turning off your computer.

Drew Dunn
[log in to unmask]

Axelrod, Marc wrote:
>
>         Just a Quick Question:
>
>         Can you damage a computer by disconnecting/reconnecting the
> printer cable (on the computer end) while the computer is on.  I think
> you can, but others are arguing with me.
>
>         Thanks for your help.
>
>         Marc Axelrod