Hi there!
Ok, so i have filled in as good as i can in your list below, mostly by memory though. I have used this computer without any problems for more than 2 years now and the only reason i wanted to change my CPU cooler is because it started making more and more noise, even after i cleaned...
I am having a weird issue i have not experienced before. I have replaced several cpu coolers before, usually without any problems. But this time it is acting weird.
I removed the stock cooler, took out the CPU and cleaned the thermal paste from it, remounted the CPU, added new thermal paste...