Toolbar has border/edge- what does this mean?

Hi.

My computer is running quite slow at the mo but I seem to have a border to my toolbar at the bottom of the screen. Can anyone shed some light as to what this is?
Would attach screenshot but haven't worked out how to do that yet.



Thanks in advance,

Woody

 

p.s.
Apologies if this is in the wrong section.
I believe it is malware related and have cleaned computer with various cleaning programs as recommended here but it still remains.