Try removing all except one stick and test that one stick
, leave it for 7 passes at each slot. After the 7 passes, move the stick into another slot and so on. Keep doing this with the other sticks also. By that, we'll know which ones are freed.
If you can borrow some RAM-sticks from a friend, workmate, colleague, or a family-member it'll be great. Be sure it's the same socket.
And remember just because the MemTest gave errors at first at a specific slot- and wouldn't do it second time, certainly doesn't mean the stick or slot is free from errors.
Luckily, RAM ain't expensive, unless your have DDR2.