What intel cpu's can be overclocked?

Only the X/K suffix chips have fully unlocked multipliers.

Non-K/X i5 and i7 have the turbo-boost clock which can add 200-400MHz and the ability to disable cores for a +1 multiplier bump per disabled core which makes very little sense unless you are running an OS limited to 1-2 cores.
 

would you please tell me how to increase 200-400 MHz in intel i5 2400 @3.10 GHz processor as you said in your comment.