1st thing i want to mention is that I have been playing windowed mode for years on this game, and yesterday I loaded the game up and the game ran choppy, showed 8fps on the in-game sys config menu.
I switched to full screen and the game ran fine, went back to windowed mode and it went back to being choppy(8fps again).

Odd thing is when I open the task manager and keep it open, windowed mode works as it should but showed 100% gpu usage.

I did a shutdown and restart of the PC, and still the same issue.

I tried a clean install of graphics drivers, it worked for the first time loading, but then after closing the game and reopening, it was back to the choppy 8fps in windowed mode.

I then took my PC and blew the dust out of it and re-seated the GPU.
Still low fps and choppy in windowed mode.

I then used DDU program to uninstall the graphics drivers and then reinstalled them from the Nvidia site.
It worked fine the first time I loaded the game, but upon closing and reopening it went back to being low fps and choppy in windowed mode.

I tried also resetting the bios settings to default, but still having the same issue.

I am unsure of what else I can try here. Like I said, I have been using windowed mode for years on this game, and all of a sudden yesterday it just started this issue with the low fps.

There were no windows updates or other updates that could have affected this either, I checked on that as well.

PC specs:
Windows 10
I7 4770K
Nvidia 1060 6gb
24gb RAM