First, you may wish to bring yourself up to speed on the network equipment in use there. Modems? Routers? Hubs? Switches? These are all potentially pieces in the puzzle.
Secondly, it may assist you to read the networking FAQ until you fully understand it (see the link in my signature).
I am sure we can help you, but you may need to do a little homework first.
For what it's worth, I wouldn't have thought a virus would have caused all of this. But it is possible.
