16Gb installed RAM (4Gb usable)

I have a asus z87 deluxe motherboard, cpu i7 4770k with 2x8gb of

corsair dominator platinum memory, running windows 7 64 bit.

It has been working fine for the 2 years i have had it, untill a few

weeks ago, when i started getting blue screen of death, sometimes a

couple of times a day, and then nothing for 2 or 3 days and then it

came back, tried to use the 2 other memory slots, still the

same, i have allso tried windows memory diagnostics tool and it

didn't find anything, the same with memtest found nothing wrong

Then a week ago when i turend on the pc, i saw that it says

Installed memory 16gb (4gb usable) when i look in resource monitor

under memory i se there is 12gb in hardware reserved, bios do

recognizing all 16gb of memory, did some google searching but didn't

find anything that worked

the only thing i have tried is
Msconfig Boot Advanced Option (Maximum Memory) what i have read

should be unchecked and it was, and Memory Remap Feature in the bios

still nothing, so i bought some new memroy 2x4gb, still the same

Installed memory 8gb (4gb usable) 4gb in hardware reserved.

But on the plus side ther have been no more blue screen of death

anybody have any ider on what to do,
i hope what i have written makes any sense,oh and sorry for my english

I had a similar issue. with my FX platform.
It might have been that I had two seperate kits of ram (both same spec)

I solved it by installing one stick at a time, boot, add another stick and somehow it got all 16.

But it sounds like you may have other issues

You may find Hiran's BootCD useful, in particular the Testing Tools. Download the whole thing or just the tools you think will be immediately useful to you. It's a kind of Swiss Army Knife for broken Windows PC's.

Link: http://www.hiren.info/pages/bootcd

SystemRescueCD also has some useful Windows utility tools for memory testing, etc.

Link: http://www.sysresccd.org/SystemRescueCd_Homepage