Seems to me there is a setting somewhere in Windows's dial-up adapter that says "Disconnect after 20 minutes of no activity" or something like that, and if it is on it will consider a download as "no activity" and pull the plug on you. And it is on by default (curse you, Bill Gates!). Incidently, you should get around 200K a minute on a 56K modem if everything is running full steam.