The frame looks like one of the old Trek singletrack steel frames, but I've never seen one with Trek written on both the down tube and seat tube--especially not in two different colors like that. I think the person may have added that blue Trek seat tube decal after the fact. It appears to have those cheap combo shifter/brake levers that come on entry level bikes. The fork was definitely added later on, and it looks like a rather nice fork. I'd ask about the components on the rest of the bike, perhaps go take a look at it if the price is right. Sometimes one finds diamonds in the rough.