USB ports (keyboard and mouse) won't work while monitor is plugged in
This is a new issue, my PC has been working fine for moths prior. When booting up with everything plugged in the keyboard will flash its lights like it is going to work but then once the Windows log in page loads the keyboard and mouse and anything that is plugged into USB ports will not work so I can't even log into the PC. The USB ports will work when in BIOS. Furthermore, when I unplug everything but the keyboard and mouse ans boot up the PC they will work and stay working the entire time, but I obviously can't do anything without a monitor plugged in and when I plug in a monitor it does not work. One problem That I can think of is my C drive was pretty much full and might be corrupted but I have no idea how to solve any issues with that if there are any.
See if this guide helps you get further with your computing experience. It looks like you're running off of an installation of Windows 10.
Can you please pass on your full systems specs? Are you sure your BIOS, chipset and device drivers are up to date? If your C drive was full then you should try and free up some space by following this guide to clean up the space occupied on your installation drive.