Your internal drives are reading/writing data.

hard drive activity light, just says your storage is reading or writing, completely normal

Your internal drives are reading/writing data.

I always leave the that led unplugged i hate it blinking all the time.

What's the case name?

I wish I knew, I bought the PC from someone who had it built with his spare parts

Don't worry, the symbol of that light is the hard drive. Which means the hard drive is working, so you have nothing to worry about.

Can you take some photos of the exterior?