Nice Gaming PC was working a few weeks ago but now is blue screening and laggy.

So my friend bought a bunch of nice parts for a nice gaming PC about a year ago and had his dad build it for him. It was working very well. Recently though, he moved across the country and now when he tries to play games, even super unresource intensive games such as minecraft, he lags quite bad. Before the move he was getting fps into the hundreds and now its spiking from 10 to 200 but is normally staying in the lows. We tried a bunch of stuff to figure try and figure it out, like updating graphics drivers, changing around settings etc. but nothing worked. Then, another problem started to arise, he started to get the blue screen of death. I knew this was bad so I had him check the fragmentation of his SSD and it was about 16% of his 200GB. So I had him defragment it and had him set it to defrag automatically every week. After that, we tested out gaming again and it was still super laggy. It wasn't only his games that were super laggy though, everything was really bogged down and super slow. So I had him get an Anti-Virus (MalWare Bytes) and it said he had 386 threats. So we removed all the threats and still, everything was bogged down and laggy. So we tried to reinstall windows, but to my suprise, He didn't have his disk! I tried to find a way to do it without a disk or an iso file but none of them worked. Then today we were trying to figure it out still, and he suddenly blue screened. So he restarted his computer and blue screened again. We kept trying to restart but it wouldn't work and every single time he would just get the blue screen of death. I told him that he needed to open up the computer and see if any if one of the ram sticks are bad, but he refused to as he doesn't know anything about computers and doesn't want to break anything. By the way he is running windows 7. I can't think of anything else that could be causing the problem as I'm 14 and not super experienced and it is hard to work on a pc that is across the country from me. Please if anyone knows what could possibly be the problem with his computer help as best as you can as he spent a lot of time working for the money to buy the parts.

Thank you.