Windows 7 - computer booted with 16 gig of ram and now wont

hi im looking for anyone who might have had the same problem as im haveing atm i rebuilt my pc yesterday and it booted fine with 16 gig of ram and was showing 16 gig loaded at the same time i was also rebuilding my sons pc.His ram had a problem and would not boot so i took half of mine out and booted his and left it till i got some more this morning .When i went to reeboot mine with the whole 16 gig again it will not boot with all 4 sims if i remove one it will boot but only says 8 gig... I have tried diffident configs of ram and slots and they all seem to be fine only it wont boot with all four sims in the pc it just hangs with a red ram light and black screen i have also tryed to mem ok button on my board with no luck thought it might be a windows problem ... i dont think so but i thought i would try this forum .. thanks in advance

Looks like the RAM you got second time is not working properly. Are they the same make and model no. as the old ones?

Try checking one RAM board at a time in one slot and check in BIOS. Isolate any RAM boards which don't work.

Next step would be try keeping first slot filled and then put one in second slot and check BIOS. If OK then insert the third memery board and so on.

You can also remove the RAM boards you have placed in your son's computer and try in your system. If they work then try the new ones in your son's computer.

hi and thanks for reply the ram sims are my original 4 i put the new ones in my sons pc but in saying that the ones i got him are exactly the same as mine i have tryed putting one in and adding and booting everything goes fine till i try to seat all 4 at once i can boot with 3 but it says i only have 8 gig ... i have tryed 3 sims in differnt slots so im asuming all the slots are fine and the sims also as they all booted on there own thats why im stumped

after more testing it seems my number 3 slot is not working as i have a sim in 1 2 and 4 and now show 12 gig def mother board prob ?

Yes, it certainly could be.

But, it is common issue we see that perfectly good motherboards throw up RAM errors when all 4 slots are populated. This can be due to variations in the voltage going to the RAM slots. People have reported clearing up these issues by going into the BIOS settings and carefully increasing the RAM voltage settings until the system becomes stable.

A warning: this is a procedure you probably want to read up on before attempting it. At least know how to recover if the system will not boot at all. You can look at overclockers websites for how to's. Or you could ask in our own Overclocking forum here.

when i put a single sim in the third slot it would not boot at all but all the other slot booted with a single sim would the voltage still be a factor?

Possible but probably not. But it is still cheaper and easier to test than replacing the MB!

One other thing to check: carefully inspect the RAM slot and module for any debris that could cause shorting. A single hair could do it.

Now that you have isolated the third slot as the culprit, check this slot for any dirt inside. Make sure the contacts are free from dust. Try blowing air in the slot to clean any dirt away and give the slot another try. Wipe the contacts of the memory card clean and insert firmly.

The reason I am asking you to do this is because it was only yesterday all the slots worked. Just give it a try.

thank you both i will give that a try today

just gave it a good blow and had a look in there cant see any hair and it still wont boot might just go with the 12 gig ra says 1 to 4 week turn around kinda stupid as there service centre is 10 mins away from me buy car