selling faulty hardware

on saturday 29 june i went to Computer Mania Canal Walk to purchase new ram for my sony vaio notebook. i was helped by a sales guy he did not give his name. i enquired about a 2gb DDR3 Ram and the price. i had brought my pc's original ram with to make sure that it was the correct one i was buying. he proceeded to show me one also a 2gb DDR3 ram(R279.99)and he also told me that that specific ram that he was selling me was taken out of a pc that was purchased by someone else and that person upgraded the ram immediately upon purchasing the pc, but me being a customer that has no idea about what goes on in the shop, for all i know the ram they gave me could have come out of a faulty pc that they repaired or that they replaced and are now trying to resell it.

i then asked him if it is compatible with my laptop and if it will work with my original ram installed as well and he told me that it is and it will. i questioned him in detail as to how instal the ram correctly and he told me the steps as to how to do it. i payed for it and went home. i sat down with my pc at home and followed his every step that he told me to do to install it. once i was done i booted up the pc and it started perfectly. i went into the system info option to confirm that the pc had picked up the new ram as well as the original ram. it should have told me that the virtual memory was 4gb but it only showed me that there was 2gb, meaning that the pc did not pick up the new ram. i then restarted the pc only to be met with whats called the "black screen of death". Basically the pc turned on, the keyboard was responding and it played the windows start up tone but the screen was dead(black) i then removed the new ram and restarted the pc only to have the same problem. i am unable to boot into the bios menu nor the windows recovery mode. i am not able to ANYTHING at all on the pc. i took it to the pc repair shop near to where i stay today 01 July and asked if they could just test it and see if they could find what the problem was. they informed me that there is a possible motherboard problem caused by the new ram that is possibly faulty. now i am sitting with a laptop that is as good as a brick and im beyond furious about it.

i have emailed computer mania regarding this issue asking them as to who will be responsible for the repairs needed and also who will be covering the costs for those repairs that are now needed and due to hardware that i purchased from them. there was absolutely no problems witb my pc before any of this. i had just made the decision to start upgrading the hardware and did extensive research as to what kind of ram i was currently running and what i needed for the pc i refuse to spend any amount to fix it as it was thier hardware item that had caused the problem to occur. i am still yet to get a answer to my email from them. my hands are up in the air now and i am now left with a laptop that does not work.