If you have a long phone line between the jack and the modem, especially if using extenders, try with a shorter distance if possible and a shorter (single) line. Try it from another jack if possible, as internal wiring at that location may be a factor.
Try checking the phone line for noise (pick up a receiver, hit a single button like '5', and listen); any noise can degrade the modem's speed. If there is any noise, call your phone company about it; though they will only test for voice quality (and noise), not modem speed. Do this after the "try from another jack" though, as many will charge for checking internal wiring.
Try disconnecting any other equipment connected to the same phone line; the more things plugged into the line (fax, answering machine, other phones, cable box, alarm system, etc.), the lesser the quality of signal to all of them. And one malfunctioning unit can mess things up for the rest.
Also, if you can't connect faster than 28.8 (with a 56k modem), there may be analog pair-gain devices on the telephone lines between you and the number you're dialing. You might try other access numbers in the area, but that's about all you could do. Analog pair-gain would also rule out DSL availability.
Try reducing the number of programs running on the computer when testing this. Sometimes that can bog it down, too.
~ Eric -- "Metaphors be with you."
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