you have tried the button on the dash, right? sorry i know it may seem like a dumb question, but a lot of people don't know at first that there's a different switch for the fogs. btw they will only come on when the headlights are on.
if that's not the case, have you messed with them in any way? did the previous owner maybe? if you don't know, there's a way to rewire them so that the headlights don't have to be on to have the fogs on, and i'm wondering if you or they tried or did the mod, because there's always the possibility of a loose connection.
the wires are pretty easy to get to behind the foglight assembly, especially if you loosen that one screw on the inside of it. i'm guessing your problem is with a fuse, the switch, or some wiring though if neither comes on. the switch pops out of the dash pretty easily with a flathead screwdirver if you want to check back there.
hth.. also i'd suggest checking out
www.g2ic.com if you haven't already.