It depends upon your connection type. For a dial-up modem connection where upld & dwnld bandwidth is combined, it will affect how much u have left over. For most other types of connections, upld & dwnld capacities are separate. Thus it should not affect your overall use whilst using the net (depending how much upld bandwidth u have.) As for affecting your overall comp., LW is like any other app & will use a certain amount of cpu & ram but it shouldn't affect anything else u do with other apps.