The point about internal modems is that the drivers for them are not exactly free. I have a dlink 560++ internal modem which i wanted to configure in linux (FC3) the drivers is available at a site called convexent or some similar name the problem is that the free version of the driver limits the speed to 14.4K and to get the full version you have to PAY. This site has almost all the drivers for internal modems working in linux but the payment factor is the problem. So the best option is to go in for an external serial modem which requires no additional drivers in linux and gives you the full speed.