So I built this PC months ago and installed Win7 on it. It ran just fine until I encountered some trouble running a few games, upgraded to Win8.1 and have all my games working. But recently Win8.1 would run kinda slow. I'm not talking about game performance as I usually have constant framerate. These problems occur randomly but somewhat persistant: Explorer would crash (stop working) when right-clicking on items/folders. Problem still persists after Explorer restarts itself. That action center flag-like icon on the taskbar would say that I have problems with virus protection etc when I already have Avira installed and updated. Sometimes a pop-up would appear suggesting me to either turn on Windows Defender or turn on and update Avira, whichever I click doesn't do anything. Sometimes CPU load would reach 100% whenever I start a game and the game won't even start at all. Some other time, the game would start up just fine and when it does, I usually have constant framerate. Windows boot up a bit slower than it should, and restarting from the OS itself takes longer time than shutting down and turning it back on again. That one time, Windows boot up and prompted me to enter my password on the login screen. When I logged in, the background was black and I got some error. It appeared as if I did a reset on the system and lost my stuff (the colour scheme was changed to default, installed programs disappeared). Opened the metro start-menu and Windows just froze. Did a hard reboot and everything returned to normal. Sometimes Wi-Fi speed is slow, compared to my Win7 laptop. maybe more but I can't remember for now... Take note that my Win8.1 is up-to-date and these problems started months after initial installation of the OS. I also did a fresh install from Win7 to Win8.1. The PC temp is usually around 37 degrees Celsius (both mobo and cpu) and I clean the tower regularly. I recently dual-booted Linux Mint 17 and the PC ran very smoothly so I doubt its a hardware issue. And I also did memtest and stress test and all that for hours and the PC didn't crash or gave me errors and temp didn't go over 90 degrees Celsius. I really don't want to re-install the OS or do a refresh as it would be a hassle to re-install all the programs and games I already have. Thanks in advance.