Help Fixing a Friends Computer?!?!

I'm fixing a friends computer, its a Dell, not completely sure what type. but the tower is sopposed to be on its side instead of standing. model no DCNE. basicly, it doesn't want to get the internet from a direct ethernet cable. I was thinking maybe its the drivers? but i really don't know and could use some help trying to figure this one out. Thanks. Feel free to ask any questions that i should've added in the first place.