Overclocking prebuilt 6400

[Andy_53]

My local best buy has an i5 6400 system on sale, and I've heard you clock overclock the 6400 despite it being non-k.

My questions is, is it possible to overclock a PREBUILT system, or is it only possible on custom motherboards. The desktop on sale is an Acer Aspire TC.

Also, is the i5 6400 sufficient for 1920x1080p gaming with a gtx 970.

 

[Zerk2012]

Usally all the overclocking settings are locked so no overclocking.
Not to mention they use the cheapest crap they can.