WHen enabling XMP mode for 1600 dram, when i right click on computyer and select properties it is saying core i5 750 2.67GHz 2.27GHz
How come it says 2.27? is this the other cores, or should I ignore it?
For you're question, i would just ignore it.
what i would trust is CPU-z and see what the actual speed is in real time.
As for why it says 2.27 GHz (or less), most likely it's Intel speedstep is what your seeing working. http://www.tomshardware.com/forum/277716-28-showing-correct-speeds
To see max speed of your cpu on windows or cpu-z, run prime95 on all cores. It's a stress program that forces cpus to run at the highest speed. if you see 2.6Ghz (or more with turbo boost) then cpu running fine.
if it's staying on 2.27 then come back and tell us.