I'm using Windows 10 Pro 64 bit on a custom built computer. Here's my specs.
I recently bought and installed a new CPU cooler (Coolermaster Hyper 212 Plus) because my stock cooler fan was very loud when playing games. I never had an issue with overheating but I decided it can't hurt to be more cool so I went ahead and bought 2 case fans (Coolermaster LEDs) and installed them as well. After installing all three fans and turning my computer on for the first time I noticed the startup was a tad slower than usual. I then opened Google Chrome to check my email and it took longer to open, then took even longer to load my email page up. I thought it was possibly my internet since it sometimes goes out or what not, but my internet was completely fine. I googled around and thought maybe that I didn't apply the thermal paste to the CPU correctly when I installed the cooler, so I took the cooler off and the CPU out, cleaned both, and reinstalled. Same issue was happening: longer loading times, slow when running any amount of programs, and my FPS was down to 60-65 FPS in R6S (Rainbow Six Seige) when I usually get around 80-100 FPS. As well as, in CS:GO I get constant screen tearing and frame drops on even the lowest settings when I usually run them on max perfectly fine.
So at this point I knew something was completely wrong. I checked all my drivers, made sure everything was plugged in correctly, but couldn't find the issue. My friend told me it could be my RAM. I took one stick out and ran the computer and it seemed to run ok, so i swapped them out and ran the other stick by itself and my computer turned on but my keyboard/mouse didn't turn on and nothing displayed on the monitor. I felt like that was the issue, so I sent those 2 sticks into Corsair and they sent me 2 new sticks of RAM. I received and installed them, and am STILL getting the same issue. I am starting to think maybe I could have fried something on the motherboard on accident by static shock. I don't see it being my GPU or either my SSD or HDD (I did a defragment on both of those).
I have AVG free and I scan my entire computer daily and AVG has not found any viruses. I downloaded Malware-bytes and ran multiple scans and found nothing as well. I received help from the Virus and Malware section of the forums and figured out this is not a Malware issue. It has to be something silly like a corrupt driver somewhere I can't find or I messed something up when reinstalling that new cooler.
TL;DR: Computer running slower than it previously did after installing new case fans and new CPU cooler (fan/heat-sink). I'm thinking it's either a bad driver hidden somewhere or possibly something to do with the processor when I took it out and reinstalled.