How do I change this pop up thingy (screenshot provided)

[Kwertie]

Hello,

I don't know how this is called, but I want to change it. The way it is now is ugly and annoying. Can anyone help?
Thanks.

Kwertie

PS: It's this:

 

[romi]

unpin it.

 

[CuriousOne]

If you mean the middle icon on the Taskbar I believe that is a folder you have open or minimized.
Double click on it should open it. Then close what opens and it should disappear.
If it is pinned to the Taskbar, right click on it and select unpin.

Hope that helps.