4gb ram memory usable out of 8gb ram in my 64 bit windows

[kacheng]

I have installed 8gb ram in my motherboard my ram is 2×4 gb 1600 mhz ram and my motherboard is gigabyte 78lmt s2 rev 1.2. After installing the ram i just check in the computer properties it says installed memory 8gb and 4gb is usable.then i check in task manager it says 4gb is hardware reserved.my os is windows 7 64 bit.why is this happening.i kbow nothing about computers please help me.
I have done this tricks but it failed
1.i go to the msconfig and uncheck the memory but it did not work.
2.i go to the bios setup and i tried lowering the memory speed to 1333 mhz but it did not work too. So please help me now what shoud i do.n sry for my bad english

 

[Rabmac]

Try booting with just 1 RAM stick. If it works then swap it for the second RAM stick. If your PC boots up both times then you know you don't have faulty RAM and we need to start looking for another cause and solution. Let us know how you get on with this.

 

[ModernWarfare]

it's either DIMMs not being seated properly or the motherboard having a few bent pins/not contacting a few pins which result in the loss of memory. try checking the rams one more time re-seat them properly.

 

[kacheng]

It says installed memory 8gb.usable memory 4gb and 4gb memory reserved.so i want to know how to fix the reserved memory.one thing i forgot to mention.my mother board is gigabyte 78lmt s2p rev 1.2 which support 1333mhz ram and my adata ram is 1600mhz.so is this the reason ?

 

[ModernWarfare]

have you tried updating bios?

 

[kacheng]

My pc wont boot up when i put single ram in dimm 2 slot

 

[Rabmac]

It looks like you may have a faulty Dimm slot. Does your PC boot up both times when you stick different sticks in dimm slot 1?

 

[ModernWarfare]

the second DIMM slot is Faulty or has bent pins. this cannot be fixed unless you just get 1 stick of 8gb ram or get a new motherboard.