Windows 8.1 can't recognize 8gb ram

Hi I'm using 8gb computer since 3 years ago
But yesterday, I found something strange.
I was using VMware, to use Ubuntu. but it was so slow.
So I checked my computer and I found the computer recognize only 4gb ram, not 8gb ram.
But I can racall that I checked my computer 2~3month ago and it said it is aleady recognize 8gb ram.
CPU-Z said it is installed that 8gb ram, but only use 4gb ram.
What is problem??

Do you have a 32 bit OS?

no i'm using 64bit os

Remove one memory stick and swap around to see whether it fixes the problem, you need to check them individually to find out if any of the stick is faulty, don't forget to seat them properly.

Likewise..... swapping ram sticks is more accurate than even running Memtest 86+.

Ram sticks in a desktop PC usually sit very close to the cpu, and dirt from the cpu fan will be blasted against the ram.
Dirt between the little legs on a ram chip can cause it to basically short out, and that chip will FAIL.

Here is just one example of what I'm talking about.


Over the years, I've saved thousands of dollars worth of ram memory, by just cleaning it. So I never throw out a piece of ram, without first giving it a bath, first in soap and water and then in Denatured Alcohol. And after a thorough drying, most ram that seemed to be bad, will work just fine again. Don't forget, to polish up those little Gold Edge Connectors.

Good Luck!
TechnoMage