my replacement ram doesnt work(immediate help needed)

hey guys just got the replacement for my ram (kingston 800mhz) and even one of the replacement does not work lols

ok but 1 thing i wanna ask is when i open cpu z it shows me that my ram freq is at 400 mhz? now correct me if iam wrong but i bought a freaking 800mhz ram

also iam giving up on kingston and ordering a corsair 800

i also wanna comfirm that is my motherboard compatible with 800 mhz coz the asus site says iam (just wanna confirm)

so in brief 2 rams that i bought were faulty got replacement for those and 1 of them is still faulty and the one iam working on is working on 400.2 mhz

some quick help needed coz giving order for corsair