RAM issue in Win 7 x64

A strange thing keeps happening sometimes. Win showed 3.9 usable of available of detected 8GB! Why? Restarted, showed 8Gb again. Next restart same issue.

I took the RAM sticks out, one by one booted fine on same slots. Normal Memory Diag. ran okay without error. Next restart same issue again Took them out inserted in 1st and 3rd, instead of previous 2nd and 4th. So far so good for 5 restarts or so. I don't know

Check the BIOS for memory. Windows only knows what the BIOS detects. Maybe A BIOS (CMOS Memory) reset is needed?

BIOS is up to date. No, these exact RAM were not on support list. But, it supports 1866MHz RAM, as does the processor. POST went fine the first time I installed.
After the slot changes after the problems, so far 8Gb detected and used. The sudden problem was it detected 8Gb but usable was 3.9Gb!

I don't know. There are lags/slowness randomly. I borrowed and changed around HDDS from my friends, after getting an SSD for OS. Same problem remains. RAM? Power seems okay in Gigabyte utility. Simply don't know.

WU is set to manual. I just installed windows6.1-kb3125574-v4-x64 convenience rollup from MS to see if it solves the problem. It did not. I tried both slot combination with RAM, doesn't make a difference really...even did a clean install before that-clicking menu items responds late often, as does getting into a hard drive partition. I don't know what else it could be... PSU?

i downloaded it (open monitor).What do you want me to do now?
(BTW, I usually use Gigabyte's utility usually, didn't see unusual temps.)