only single channel ram works

Hello, I bought a new ram for my old computer. But when I put only a the 4gb ram (new) it will open a bit and automatically turn off. But if I put 2gb ram (old) it will be boot up so fine. Also, I experimented to put them together and it boots up but the problem is the bios only detect 2gb ram...

So the other day on my Sony VAIO SVE14A35 I noticed that my 'c' key was typing 'v' every time. Didn't really do anything out of the ordinary, although I did visit a spam link for kicks that was skyped to me (a webcam site), and I did notice the problem soon after that. Honestly I really doubt...