Well, I'm no Simcity Master, but the region you download should be a folder, or maybe a file. Either way, I'd guess you go to My Computer, then to the place that has Program Files ( might be (C: ) drive for most). From there, go to Program Files, then Maxis, then Simcity 4, then there should be a folder called Regions. In there should be some folders with names of some Simcity 4 Region names inside. That's where the file(s) go(es). Hope that helps.