Strange iMac internet speed problem

I had high speed cable installed 2 weaks ago and have been fighting with
them over slow speeds since. I signed up for the 4.0Mbps service and
the fastest I have got is about 2.5 They have sent line techs out several
times and everytime they tell me there is nothing wrong and they are
getting 5.0+ speeds at the pole.

I have been waiting for Apple to come out with the new PowerBooks but
so far they haven't so I bought a nice but inexpensive ($1200) HP laptop
running XP Home for now untll Apple gets off their butts.

I plugged the cable modem line into the HP laptop and was totally shocked
at what I saw. Almost every speed test page gave me 3.5+Mbps every
time. I unplugged the network cable and put it back into the iMac and
ran several tests getting the same 1.5-2.5 speeds, switched back to the
HP and 3.5+

I checked all the settings on my iMac, energy settings off and CPU set at
highest speed. Networking is networking either on Macs or PC's so does
anyone have any ideas ? I am totally lost on this one



P....