I remember on my Desktop computer in Hammer I did something and the texture that was on the side changed to "/paint..." every time Hammer booted up. Now it is the default "anim_wp...". Does anyone know how to make it like my Desktop with the 4x4 paint texture (whatever it was)? I want to do this just so it doesn't look odd every time I use Hammer on my laptop.

By default, it should be anim_wp. I don't know what you did to set it as /paint, but anim_wp is the default texture because it starts with "A"

The texture for paint type number 5 is in the materials root, so it's sorted before anything in a subfolder.