Returning a Defective Product

I bought my son a Alienware computer for school and ever since he got it he had problems with it.  So we called Dell tech team and they said to reset the PC and we did but the problem came back, after a few months and resetting the computer more than 4 times I decide to take action and someone finally was able to get a new CPU and GPU to fix the computer and that didn't work.   And I'm fed up, I called for a return, stating that the problem never resolved and was made aware to you guys during the return period.  And the lady said no it not possible and I replied then you should have made the situation aware to us because the second guy said that there might be a hardware issue and did nothing to check if there was.  I filed a complaint to BBB because, it a headache to go through Dell Tech department and then they say reset the computer and the problem returns.