I can only guess you read or saw something about editing the registry to optimize throughput. You did not mention your operating system, however. There are some tweaks or utilities that will do this for you as I recall with Win98. I cannot speak for XP. The result obtained might be disappointing, however. If you are unfamiliar with the registry and editing it, there is a caveat. You can do harm by making a mistake. You need to back it up first. If you wish, you can post more about what you heard and where. You can use Google key words to search for sites that might help. Words such as modem, speed, registry, tweaks, should get some hits. Good luck.
If you download the file utility tweak they give you tips on how to speed up your modem. One of those tips is to go into a file on your computer and change the com numbers to something like 981600. Could you tell me the file to do that and if that is the right number?