[Suicide Junkie]

Simplest things first:
Power off everything (unplug router and modem) leave for 5 minutes.
Power up in order from the wall;
1) modem (Wait for the blinkey lights to show Online, ready or whatever arcane symbol means its connected.
2) router (Again wait for the blinkeys to settle down to connected state)
3) turn on computers.

Further questions:
What kind of internet connection do you have?
What kind of "re-installing" were you referring to before?