3 months ago, I bought a second hand graphic card and installed into my computer, since then i have been experiencing randomly computer freezing when playing game. It's strange because, not like the other cases i came across in this forum, the sound still very normal no buzzing sound when the screen freezes and I cant do anything to escape to desktop. I try mouse and keyboard with Alt+Tab, Ctrl+Escape but everything doesn't respond at all (I notice that when I try to press numlock, caplock, the light of these buttons doesn't budge) eventually, i have to hard reset my pc. I scan my computer hardware for problems in Device manager but the computer shows that the devices are working properly and no conflicts found, I always update my graphic driver and even reduce the cpu speed to the smallest value, but it still randomly happens to me. I really have no idea what is going on. Here is my specs and hope you guys smell the rat for me.
CPU: Core i5 3570 (not 3570k) @ 3.4Ghz
OS win7 64bit
Mainboard: Gigabyte socket 1155 - H77M D3H
PSU: Acbel G500W pcb027
GPU: geforce 9800gt galaxy edition 512mb
Thank you million times!