SOLVED
So even though I was in High Performance power setting through Windows, one setting was still throttling my CPU.
To fix this, I went to Windows power options. Clicked "Change Advanced power settings"
Scrolled down and opened Processor Power Management > Maximum Processor State
This value was set to 5% for some odd reason. I cranked it back up to 100% and BAM, my problem was solved.
Original Question
So some background. I had this problem before and the only way I was able to fix it was to reinstall windows 8.1
Anyways, I built a new rig a while back with these specs:
It's been awesome and I frequently play Battlefield 2 (a modded version) and World of Warships. Both games run flawlessly at 60FPS.
However, I turned my PC on today and they both are unplayable due to lag (averaging ~5FPS). Even the in game menus are laggy.
Windows 8.1 Task Manager isn't helpful as nothing seems out of the ordinary.
However, when I downloaded MSI Afterburner, it's showing my CPU usage at 100% even when I'm sitting in the menus. (GPU usage is around 30% and temps of both CPU and GPU are between 30-45c)
Here's screenshots of MSI Afterburner CPU usage vs Windows 8.1 Task Manager:
Does anyone have any idea why this could be happening? Is my CPU going bad, or is this due to a software issue?
So even though I was in High Performance power setting through Windows, one setting was still throttling my CPU.
To fix this, I went to Windows power options. Clicked "Change Advanced power settings"
Scrolled down and opened Processor Power Management > Maximum Processor State
This value was set to 5% for some odd reason. I cranked it back up to 100% and BAM, my problem was solved.
Original Question
So some background. I had this problem before and the only way I was able to fix it was to reinstall windows 8.1
Anyways, I built a new rig a while back with these specs:

It's been awesome and I frequently play Battlefield 2 (a modded version) and World of Warships. Both games run flawlessly at 60FPS.
However, I turned my PC on today and they both are unplayable due to lag (averaging ~5FPS). Even the in game menus are laggy.
Windows 8.1 Task Manager isn't helpful as nothing seems out of the ordinary.
However, when I downloaded MSI Afterburner, it's showing my CPU usage at 100% even when I'm sitting in the menus. (GPU usage is around 30% and temps of both CPU and GPU are between 30-45c)
Here's screenshots of MSI Afterburner CPU usage vs Windows 8.1 Task Manager:


Does anyone have any idea why this could be happening? Is my CPU going bad, or is this due to a software issue?