These are most often available free of charge from your modem manufacturer's web site. If you don't know the correct website for your modem manufacturer, check the documentation that came with your modem. If you are experiencing random dropped connections, try turning off data compression. With modem.inf being used, Windows may or may not send the correct command to disable data compression. If this happens, read your modem documentation and enter the AT command to disable data compression.
Modems have limited buffer space for both error correction and data compression.
Error correction is necessary to provide an error-free connection. Also, when errors do happen, modem buffer space is needed to correct them. Modems have error thresholds that, when exceeded, will cause serial overruns and will hang up the call, resulting in a disconnection. These are often indications of line noise. It can be caused by faulty wiring, moisture, and several other factors.