Never seen a adsl 2+ modem work on 5v before.
The normal 9/10/12v modems consume around 10watts
Don't screw with your laptop USB ports. Consider an average nokia/motorola mobile adapter. Most of them are rated 5v. You can pick one up from the streets for 50 bucks. Cut the wire in the middle and solder the adapter plug to it. 5v is not enough power to fry your modem. There are just two wires you need to experiment with.
The normal 9/10/12v modems consume around 10watts
Don't screw with your laptop USB ports. Consider an average nokia/motorola mobile adapter. Most of them are rated 5v. You can pick one up from the streets for 50 bucks. Cut the wire in the middle and solder the adapter plug to it. 5v is not enough power to fry your modem. There are just two wires you need to experiment with.