Your GPU might be having problems, but the other problems you list sound like either a bad hard drive or a virus / bad windows install.
There are several utility programs you can download that will check your hard drive for failures. I would back up any important files and then run those. If the hard drive is bad, replace it. Either way you will probably want to re-install windows from scratch.
Any good beginner guides for identifying broken parts in a desktop computer ?
I’ve recently bought a used computer, and it has a few problems. I’m looking for a guide to help me identify which parts are causing the problem....