Try this. Unplug your modem at the PC and delete the device in Device Manager. Switch your PC off and remove it's power supply. Reconnect your modem then switch the PC back on. If you are using Win98 or greater the PC should recognise a new device and try to install it. If your modem is fairly common your Windows installation disk may have the drivers on board. If not it is a fair bet that the original drivers are somewhere on your PC. When the install routine asks for a particular file use the search option to find the file. It will probably be in C:\Windows or C:\Windows\System32.