you can get more out of your serial connection and gets your modem working its fastest with the help of Device Manager.

Go to Control Panel > System > Hardware > Device Manager. This will show you a list of all the devices attached to your PC. Look for the Port (COM) communication port. Right click and select Properties, and click the port settings tab. Increase the bits per second from "9600" to "128000" and Flow Control to "Hardware". Then, click on the Advance tab and set the Receive and Transmit buffers to Maximum. Click OK and close all Windows.