Getting Low or variable FPS on games Please Help

[LeHerpDeeDerp]

I've had this problem of getting low fps before, but it was solved by replacing an old HDD that had a virus that greatly raised my CPU usage and couldn't be removed with any program. I first learned I had the original HDD problem because I plugged in my friends HDD into my system and it worked great, so I know my system can handle the games. After I replaced it I was getting much better FPS and CPU usage such as 90 FPS on BF4 with only 70% CPU usage, but now it's slowly getting worse. On BF4 it's anywhere from 30-80; Minecraft is 15-100 and anything else I play is basically the same variability. I've updated all my drivers, optimized my games and specs, but it's not working. I also have a friend who has a 3 year old AMD card, and he claims he gets a constant 100fps on MC while mine fluctuates. Does anybody have a clue on how to fix it? Because I don't want to know that I have another hidden virus, and I've been to Tiger Direct and they basically told me to screw off because I didn't have the Windows sticker on my rig, and I don't trust BestBuy with anything.

Specs:
Windows 8.1
CPU: i5-3570K
Graphics: GTX 760SC
Motherboard: ASUS P8Z77-V LX LGA 1155 Intel Z77
HDD: 1TB WD 7200rpm
PSU: Corsair CX750 Builder Series
RAM: 8GB Corsair
CPU Fan: Stock Intel fan (I also have a Cooler Master Hyper 212EVO to switch if needed, but it just barely fits in my case)

[Shd0w2]

Do the HYPER212 regardless

[x Relentless Xx]

With a stock intel cooler your CPU might be getting too hot and start to throttle itself

[RubyRoks]

replace the cooler...or at least the thermal compound...and update us
in my experience, just this helped frame rates in WoW and ArmA and it also kept my GPU from spontaneous combustion (the damn thing reached 101 C after 30 minutes of playing WoW)

[ig33ku]

If there was a virus on the old hdd and you connected a new hdd while that old hdd still plugged in the virus has then spread to the new hdd despite you install a AV on it. I recommend unplugging your old hdd, formatting your new hdd, reinstalling windows and get 360 internet security. Do all the updates for your windows and 360. Then install your games.

 

Then if it is possible use the windows backup app and make an image of your fresh install on another clean hdd, the reason is after doing that you can now attempt to purge your old hdd by formatting it then scanning it with 360 or just scanning it with 360 if you want to save files on it.

 

Best method is to have a usd hdd dock to do this otherwise make sure that in bios you boot to your new and protected hdd otherwise booting to the old infected hdd which will load windows will allow it to access your new hdd and infect it. Make sure that the backup windows image hdd is not connected to pc when you want to start this purge.