external 56k modem-doesn't move for long time periods

Hi;
I have recently installed a zoom 56k external modem.
I have it attached through the serial port on a pent2.
I purchased it for faster internet of course, because I am very rural
and can access only through slow dial-up.
But I still seem to be uploading web pages slow, the modem just sits
there and doesn't move for long periods of time.
However I also have a pent4 which has an internal 56k modem,
and this doesn't happen to it.
My Pent2 is 450MHZ with 128megs Ram, and the Pent4 is 1.7GHZ with
256megs Ram.
Does anyone know what is slowing the Pent2 modem? Is the Pent2 just
too slow of a CPU or not enough Ram? I always thought that
external hardware modems were faster. All the settings seem fine
-could it be other things running in the background that are using the
comp. RAM or what??? If so, how do I track the culprit? I just can't
seem to figure this out!
ANY advice on this matter is appreciated!
Thanks,
Jinnie
BTW-they both use the same phone connection box, so I don't think it
could be line noise affecting the one and not the other.