I have been having some strange problems with my desktop that didn't make any sense. The biggest one was trouble starting up. Sometimes it would boot, sometimes not. There were random useless Windows errors about boot files being missing or corrupt, along with other red herring stuff that made me look in the wrong places. Sometimes it would part-boot, then just stop. It seemed very inconsistent.

Today I finally had enough and started going through it systematically. I now think I have found the problem. Time will tell, but I'm pretty sure. 

The problem is a Sata cable. I have had trouble with them before. Some had seemed unreliable in the past and one even shorted out and nearly burned down my house. But I didn't think about it that much. I just replaced the cables and moved on. 

Now after this last episode, I have replaced the cable again, this time with a better one that has a solid locking connector. The other one did not and was loose. 

So far this appears to have fixed the problem. While working my way through this, I have been surprised by the very bad quality of many cheaper Sata cables. They are very flimsy and don't always make good connections. If they are not locking types, they can work loose very easily. In the good old days of discrete components and IDE drives, the connectors were practically welded on. It was simply impossible for one to come loose or break down on its own. These days, hardly anything seems to be made to last. 

I mention this for what it's worth. If you start experiencing strange issues, look at the cables before you start replacing the RAM or CPU. You might be surprised what you find.