HELP!! RAM problem

[theVoidOne]

i have 6GB of ram, but under performance in windows task manager, it says i only have 4. In system, under installed memory, it says 6 GB(4GB usable). i have 6 slots and im going to put ram in 1 3 and 5. the problem is slot 5. i tried different combination (all my rams work) and i found out that if i put a ram in slot 5, it become "unuseable". i built my computer last week and when i first built it, all 6 gb worked. this is driving me crazy, i really need help! what do i do?

 

[NoNameNY]

Which version of windows are you running? Also is it 32 or 64bit?

 

[theVoidOne]

64 bit home premium

 

[MindoverMaster]

What is your motherboard? Do you have duo or triple ram? what type?

 

[theVoidOne]

Newegg.com - EVGA 141-BL-E757-TR LGA 1366 Intel X58 ATX X58 SLI LE Intel Motherboard

Newegg.com - G.SKILL Ripjaws Series 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL8T-6GBRM

mb evga sli le
ram g.skill 6gb 1600 ripjaw

btw, before, only 2 gb worked, but i reinstall them and 4 gb work now