Upgrading ram weird problem

So I have a Macbook Pro (mid-2009), that currently has 2x2gb ram in it (4gb). A friend just bought a new macbook with 2x4gb, but upgraded to 2x8gb so he gave me the two new sticks of ram (4gb each).

When installing the two new ones I have incurred a strange problem. I stick the two new rams in there and try to boot my macbook and all it does it beep at me. I looked it up and it signifies a problem with the ram which was expected.

Anyways this is where it gets weird, I can leave one stick of 4gb ram in there with one of the 2gb sticks of ram and it boots up to 6gb of rams. I have mix and matched both sticks of the 4gb in both different slots and each works perfectly fine when paired with a 2gb stick of my old ram.

However, whenever I install both the two 4gb sticks on my computer, it will not boot but only beep at me. I have repeatedly made sure I have pushed them in all the way and installed correctly but it doesn't work.

Any suggestions?

 

Ok guys I figured it out. My computer runes 1067 MHz and these are 1600 MHz so my computer downclocks the one stick when running it with the 2gb stick. However I think I will just install the old ones in there since it isn't recommended to run it like this.