After building the PC have you stressed tested it to make sure all components function. Usually when building a PC I will stress test it for 24 hours after at stock speeeds to make sure everything is functioning and stable. Also have you installed all the latest drivers for your mobo/chipset, the ones included within the windows install are usually not the best ones and you would be better getting all drivers direct from the manufacturer.
Prime95 is a good tool to run that will stress test your new PC, it will also give you an indicator as to the max temps you will get if you plan to overclock
Goodluck