PC acting up recently. Now almost unusable.

[CrimStar]

Yesterday I tried launching Far Cry 4 as usual. The main menu popped up, so I clicked continue single-player. Then the game froze while loading. I tried other games, with similar problems. I tried looking for solutions from updating my drivers to reinstalling the games. I finally reinstalled Windows 10, but then it got really bad. The PC is now horribly sluggish. Every once in a while, large, black bars appear at the bottom and right of the screen blocking most of the display that can only be fixed by restarting, and whenever launching a game, instead of freezing, they just go to a black screen. Can someone please help?

 

[Colif]

what parts are in the PC? What graphics card do you have?

does it happen in safe mode?
boot from installer, on 2nd screen after languages, choose repair this pc, not install
choose troubleshoot
choose advanced
choose start up options
hit the restart button
choose a safe mode (it doesn't matter which) by using number associated with it.
PC will restart and load safe mode

did you install graphics drivers after installing win 10? Can try removing them or perhaps look in device manager and see if GPU is recognised
right click start (In safe mode)
choose device manager
see if any unknown devices