Question why do all my games look grainy and pixelated?

Welcome to the forums, newcomer!

Please how do i fix it?
Let's start with your PC's specs. Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model. BIOS version for your motherboard at this moment of time.

Following that, please mention the titles you're taxing the system with. Where did you source the installers for the games?

Including an image/video of what you're seeing would also lend more info to your predicament and subsequent solution to your issue.
 
in windows, bottom left of you screen, click search, type "system information", this will give you a list of your components, take a screen shot and paste here...

should look something like this (example only):

107290d1477253035-see-system-information-windows-10-a-system_information.png