Fan runs on high all the time, even on first startup

[XPbreaker]

I've got an HP XP pc that the cpu cooling fan runs on high as soon as the pc boots up. I pulled the side cover off to see if the fins were dirty but they are clean, plus it does it on a 'cold' startup. This started after I left it on all night a few days ago. I also noticed that it is slightly slower than before. I have run my virus scan and Malwarebytes but no change.
I'm affraid there is a cootie in there somewhere, where do I start?

 

[esbo]

Look at the cpu usage and what is causing high cpu, assuming it is high cpu.
If it is not then well, thats a problem more serious.