Please see the below which is my canned text for as to how to physically test the RAM on a computer, it will hopefully explain what I was getting at;
How to physically test your RAM.
The following checks require the computer case to be opened so take the following safety precautions 1st, disconnect the power cord from the wall socket, press the case power button for twenty sconds or so to get rid of any residual chrge in the system and then take anti static precautions before touching anything inside, you can do this by touching a bare metal part of the case or PSU or if a notebook by touching a household radiator or associated copper feed pipe.
Have a pencil and notepad to hand.
Remove each stick of RAM and blow out the memory slots.
Insert the first stick of RAM in memory slot one, reconnect the power and in the case of a desktop computer the video to screen cable.
Power up the computer and see how it goes.
Make a note of the results.
Repeat the procedure until the first stick of RAM has been tested in each memory slot and the results written down.
Remove the first stick of RAM and put it to one side on top of a piece of paper with the number one on it for identification purposes.
Repeat the procedure with all RAM until each stick has been tested in all slots, the results written down and the sticks identified numerically.
Now the really long winded part;
If no individual stick of memory or slot on the MB has an obvious problem all of the above needs to be repeated but this time by running Memtest 86 for each stick of RAM and in each slot on the MB and for at least 4/5 passes, for some reason that many of us cannot explain a stick of RAM may work in one slot on a MB but not in another.
Please note that some MBs (motherboards) will not boot unless there is RAM in slot one
so please provide us with your motherboard details, brand, model name/number and any revision number, these details may be found by the CPU, between the PCI slots and/or around the edge of the motherboard, once we have the MB details we can look for the user manual