HP Pavilion 590 AMD A12 MT Desktop (Open Box)

I rec'd the PC early Dec 2019 (a Xmas gift for my grandson). I had a HDD failure only one month later, but it was cheaper and faster to buy a new HDD so I bought and installed the replacement HDD and barely one month later the computer power supply died. I asked CTGINC to replace the Power Supply. Communications have caused the calendar of events to run over 90 days now. However, all the failure on both the HDD and the Power Supply occurred well within the 90 days of receiving that PC. It seems SURE that CTGINC wants to start a customer relationship and reputation of NOT BUILDING A COMPUTER to last more than 30 to 60 days? I paid $400 for a "rebuilt" computer, when for that price I could have bought many other comparable computers and some with the same specifications but vendors with lesser reputation. I trusted CTGINC and I trusted Amazon and this computer has been junk and a nightmare. In order to make this "right" all I am asking for is what is obviously "fair" and that is to give me a replacement Power Supply. Now CTGINC has told me to go piss off b/c the 90 day replacement period has passed. That makes me feel disappointment and angry at CTGINC. I can only hope that they will please reconsider their denial of my request for a power supply so I can get my grandson's computer back up and running for him. It's been "down" and inoperable more time than not since I bought it and that is not the reputation that CTGINC should be proud of.