CPU slowing down?

[tmxtom]

I have an i5 6400 in my system,recently I feel as if it may have been slowing down and sometimes it skyrockets to 100% in games, the numbers don't make sense,it doesnt add up to 100,I've done a full virus scan and it came back clear,I don't really know if its a rogue app or something?, please could someone help,I would appreciate it

 

[geofelt]

If your cpu cooler has come loose that can be your problem.
A cpu will reduce the clock rate to prevent damage.
What is your temperature at idle?
If it is more than 10-15c. over ambient, that could be your problem.

In case you need it:
----------------how to mount the stock Intel cooler--------------

The stock Intel cooler can be tricky to install.
A poor installation will result in higher cpu temperatures.
If properly mounted, you should expect temperatures at idle to be 10-15c. over ambient.

To mount the Intel stock cooler properly, place the motherboard on top of the foam or cardboard backing that was packed with the motherboard.
The stock cooler will come with paste pre applied, it looks like three grey strips.
The 4 push pins should come in the proper position for installation, that is with the pins rotated in the opposite direction of the arrow,(clockwise)
and pulled up as far as they can go.
Take the time to play with the pushpin mechanism until you know how they work.

Orient the 4 pins so that they are exactly over the motherboard holes.
If one is out of place, you will damage the pins which are delicate.
Push down on a DIAGONAL pair of pins at the same time. Then the other pair.

When you push down on the top black pins, it expands the white plastic pins to fix the cooler in place.

If you do them one at a time, you will not get the cooler on straight.
Lastly, look at the back of the motherboard to verify that all 4 pins are equally through the motherboard, and that the cooler is on firmly.
This last step must be done, which is why the motherboard should be out of the case to do the job. Or you need a case with a opening that lets you see the pins.
It is possible to mount the cooler with the motherboard mounted in the case, but you can then never be certain that the push pins are inserted properly
unless you can verify that the pins are through the motherboard and locked.

If you should need to remove the cooler, turn the pins counter clockwise to unlock them.
You will need to clean off the old paste and reapply new if you ever take the cooler off.
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[tmxtom]

Right mate,I've checked my temperatures, with nothing apart from core temp running they are at around 30,thing is its prebuilt if I unscrew it I will void my warranty so I've messaged the place that made it and I'm still in warranty