Several different kinds of memory not working in an older laptop

I have a friend down the street who has a Compaq Presario R3000 laptop (a real barnburner, right???) that is running very slow. He asked me to look at it for him to see if it could be made to run faster. It has Windows XP home edition; looking at “My computer” it says “256 MB of RAM.” Well, there’s the problem. I open up the back, and there’s NO memory DIMMS, at all! SO I tell him some extra memory should cure the VERY slow performance. Well, I’ve tried memory from 2 different sources (HP doesn’t directly sell memory for this fossil). Why does this machine seem to refuse to see any memory installed besides what’s on the system board?