|Or... Perhaps simply remove all but one module/stick and see if the one remaining produces the error messagenwhen system booted up? If it does, then likely that module is faulty. However also test each module in turn by having installed solo..., regardless of whether or not the first one produces the error... And logically, if the first doesn't produce the error, then likely it's ok; and so on...|
Memtest can take a while... Which is why the simple test each module as above may be quicker, easier? And I have know it to pass modules - yet one was faulty or at least intermittently so...
Also be simply removing each module and re-inserting it may clean the contacts, and it may simply be oxidised contacts that's the problem? It wouldn't hurt either - if you remove modules, to clean contacts on each one - with a soft eraser (as used with pencils); don't use anything abrasive... And do NOT try to clean the sockets that way... (which recently someone did...)
When re-inserting modules, perhap re-insert and remove a couple of times; as this will help clean the sockets too?
When removing/re-installing RAM... Ensure all power is disconnected - the battery too with a laptop!